Mac Upgrades/Repairs | Storage | Video | Audio/Home Theater | OS Updates/Tips/Wi-Fi
G5 Tower Random ShutdownsReturn to News Page
Feedback on G5 Tower Random Shutdowns
Reports Last Updated: 11/26/2010

This page has reader feedback from G5 Tower owners in reply to this post in a (2006) news page:

"A colleague at work asked me about purchasing a new computer, and I was able to convince him to switch to a mac from a lifetime of PC use. He ended up buying a new dual core 2.3 G5, everything stock....
When I asked him how he liked his new mac, to my shock he turned out not to be pleased, and justifiably. He is having major problems with his power supply, and he he said he's done a little research and it turns out other users are having similar problems. I'm very surprised because I keep up with current mac news and I have heard nothing about PSU problems in dual core G5 powermacs--I was even thinking about purchasing one myself. I do know they changed the PSU when they went dual core in October, as the connector is non-standard.

His main problem is that without any warning, the G5 will shutdown while in use. The sudden, unexpected shutdowns seem to be completely random.

I would greatly appreciate it if you could post a note asking if anyone has experienced any problems with their dual core G5 powermacs. From what I've read on one Apple discussion forum, Apple seems to be trying to avoid the issue and has not provided the best customer service to customers that have had G5 dual core PSU problems.
(I asked Scott if the friend had contacted Apple support and if they'd suggested things like resetting pwr mgr, or checking system logs for info (such as a "PMU forced shutdown, cause = -122" error in the log). With liquid cooled G5s, also check for coolant leaks which have been reported from time to time.)
My friend wasn't in the office today, so I don't know if he contacted Apple support over the weekend. I'll have him take a look at his logs when's he's back, hopefully tomorrow.
Thanks, Scott "

(Update: In spring 2007 Apple posted a kbase doc on Xserve: Unexpected reboot causes (No longer online), that also mentions the "PMU forced shutdown, cause = -122" log entries (in /var/log/system.log) that G5 tower owners with the 'random shutdown' problem have often seen.) Run the Apple hardware test from the system DVD also, although some that had the problem said that didn't show an error, one reader said it did. Also look inside for any evidence of a coolant leak if your G5 tower is liquid cooled.
NOTE: IF you have this problem and are using an UPS, test with the G5 plugged directly into an outlet (not the UPS). Although most didn't mention using an UPS, an defective/under-rated UPS has caused problems for several G5 owners but if you're having AC line problems (dropouts, sags, etc.) a direct connect won't solve that of course, but at least you're isolating out the UPS. (I've had an iMac G4/700 instantly shutdown on a minor power blip - the APC UPS didn't even alarm on that. The lights in the room barely flickered and if they'd been off, I'd have thought the iMac had a random shutdown.)
For those with the problem, also check the system's logs to see if there's any useful info - a common error is "PMU forced shutdown, cause = -122" and one reader mentioned "thermal runaway" errors. Reset power manager suggestions were also mentioned (shut down, disconnect AC power cord for a few minutes) but not sure that would really help depending on the root cause of this. (There seems to be no one common cause for this - but several readers with the problem said setting Energy Saver performance to "Reduced" mode solved it, but that should not be required of course.

Reports from those that saw a similar Problem:
(most recent first, see below for many reports from G5 owners that didn't have a problem.) If you do have the problem and nothing mentioned helps, if it's under warranty of course contact AppleCare for service. (Although not likely at this point, this page was originally posted in 2006 when some user's Applecare was still in effect.) If using an UPS test without it - i.e. system connected directly to wall socket AC power just to rule out the UPS as a factor. (I once had a little-used UPS that failed to catch even a line blip - instant Off on any dropout that barely flickered house lights.) Also if your G5 is liquid cooled, check for any leaks from the cooling system. (There's a separate page here on PowerMac G5 LCS leaks, failures and repairs.)
Also check to see if you have "PMU forced shutdown, cause = -122" log entries in /var/log/system.log (you can view logs in Apple System Profiler). Shutting down/disconnecting the AC power cord for several minutes will reset the SMU (there's also a reset button near the Memory slots IIRC). (Note: Also see post from Nov 2006 below on PowerMac G5 Pwr Supply repair extension program affecting some models, although Apple mentions power-up problems (not random shutdowns) as a symptom.)

Check Motherboard Pwr Supply Connections: I've had two readers say that a not fully seated power supply connector on the motherboard (near the dimm slots or motherboard battery) was the cause of their random shutdowns. Reseating the connection fully seems to have solved the problem they said. (If you don't want to disconnect/reconnect try pressing down on the connector to make sure it's fully seated.)
Energy Saver Performance Option Workaround: If that does not help, try using the "Reduced Performance" option in Energy Saver - that has helped for some, although that's not a preferred workaround it's worth a try. (BTW: An old tip years ago for G5 Tower high fan speeds after some updates to was to toggle the Energy Saver performance setting (going back to "Highest Performance") - one reader said that also seemed to help with his shutdown issue - but a later report said it was not a cure and regretted trying it. See reports below.)
FYI: For owners of Liquid Cooled G5 Towers, I'd suggest checking regularly for Coolant Leaks also ref our page on PowerMac G5 Coolant Leaks/Repairs page.)

(added 11/26/2010)
"Re: PMU forced shutdown, cause = -122
This is a report about G5 Tower Random Shutdowns. I've had ApplePMU::PMU forced shutdown, cause = -122 for years.

Today, out of the blue, I seem to have found a solution. The culprit seems to be a faulty clock and Pram battery. Even if the internal clock functions regularly, a lower voltage from the battery could cause all kinds of strange behaviour. (I never had the G5 tower shutdown/PMU error but have seen many odd problems from corrupted pram (freezes, even once no video on a PB G4). I replaced the battery today and was able to run 5 youtube videos simultaneously, with processor speed to automatic and did not have any shutdown.
You may add this piece of news on your page... Hope this helps somebody else!!!
Cheers, Mr Michele From Italy."

I asked he report back if the PMU issue re-appears later.

(added 8/17/2009)
"My G5 1.8GHz PowerPC recently began randomly shutting down, anything from 2 to 60 minutes after restart. Usually just went black and shut down; once or twice rebooted spontaneously. I tried all the obvious fixes - checked for bad caps (none), blew out dust from fans and checked that they worked, installed a temperature monitor, tried to reinstall the OS but always interrupted by crashes. (Did you reset the PMU? (shut down, disconnect AC power cord for a minute or two). Interrupted/incomplete OS installs could create even more problems as well.-M) Took it to the Apple Store and got the OS installed, then of course it worked fine and didn't crash. The 'genius' there reset the PMU in case it was that.

Came home, set up, and the crashes continued as before.

What was different about my home environment? Hotter than the store, yes, but the temp readings I was getting were not extreme. What about peripherals?
(Did you check the console/log messages to look for any related entries (such as the common (for this issue) others saw like "PMU forced shutdown, cause = -122" and some saw "thermal runaway" errors. And disconnecting the AC power cord (which you did to take it into the apple store) also resets the Power mgmt unit. However the problem repeated after you got home.-M)

So I disconnected the WACOM Intuos 2 XD-0608-U tablet which I always use, and worked with a mouse for a while. No crashes!
Reinstalled the WACOM driver (I used the latest from the WACOM website), and despite intensive Photoshop work, it hasn't crashed since. Thought this might be of interest.
(and he later wrote)
Since I last wrote - nearly a week - I've been using the computer heavily, running many different apps at once, and no sign at all of trouble. What a relief!
-Dave B."

Hope it stays that way - but if the problem repeats, on the next boot open the console and show all messages then look at the earlier entries (around the time of the shutdown) to see if there's any related messages. (Odd that a usb device driver would cause a shutdown.)

(Updated 7/22/2009, original mail from May 19th, 2009)
My June 2004 PowerMac G5 2.5 GHz was sent to Apple Japan because it just shut down and would not Boot again. They charged me their flat fee of 51,450 Yen on delivery at my door. They never contacted me they just fixed it and returned it. However, I received the copy of what they replaced
    661-3165 Multiprocessor, 2.5 GHz, w/LCS
    661-3234 Power Supply, 600 W, Grommet

I priced these parts on Google, the lowest price I could find was 500 dollars for the first part and 200 dollars for the second part, no labor. (You can get it cheaper used) that's about 70,000 Yen no labor. I purchased this computer in August 2004 received Sept 2004 I guess you must pay in Japan for a 4 1/2 year old computer.
Just thought I'd let you know,
(Update - here's his latest mail/follow-up from 7/21/2009)
This is just a short follow up, after the G5 came back it broke again within 3 months (Will not boot up, just makes noise only, Again.) Now they're going to fix it for free this time, it will be picked up July 23rd. Believe me when I say this machine while fast in it's day is a real Lemon. (IIRC, if a system is repaired 3 times for the same problem, you usually are entitled to a new replacement-M).
When it does come back I will be writing a nice letter to Apple explaining that I have been a long time Mac user, however this is the worst computer I have ever purchased, totally unreliable and the 500 dollar fee to fix it (last time) was not appreciated. I could never detect leaking fluid visually, however this thing can cook food with the heat it expels.

Brian also questioned if the problem could have been coolant leak related. It's too late now, but if I had an LCS system, I'd have done some internal checks for evidence of a leak before reporting the problem to Apple initially. (Including the 'cover side down' tip noted on the PowerMac G5 Coolant Leaks/Repairs page here.) If an internal check (after disconnecting AC power cord) doesn't appear to show any sign of a leak, try taking the side over off and place the tower with open cover side down for a day or two - then check to see if any coolant fluid is seen.) And again as noted in red here since fall 2007 - every LCS owner should regularly check for leaks (to hopefully spot one before it does major damage.)

(added 8/26/2008)
"First, thanks for your site, I've been reading it for ages! Second, I've got a Quad G5 (Late 2005), which runs quite hot, but not unusual, given what I've read. Under full load: (Most of the CPU temps (except B2) are not really that high considering full load and 1 core is always going to run hotter than the others typically.)

  • CPU A1: 50 degrees C
  • CPU A2: 70 degrees C
  • CPU B1: 60 degrees C
  • CPU B2: 80 degrees C

Idling all cores report between 40 and 50 degrees C.
I usually run distributed.net's dnetc to put full load on all cores which is scheduled with a nice value of 20. On Tiger, a process with such a low priority doesn't ramp up voltages and currents to their maximum level, while on Leopard, it does. Still, on Tiger it runs slightly faster:

    Tiger (10.4.11?)
  • Reduced: 9.2 Mkeys/s
  • Automatic: 9.4 Mkeys/s
  • Maximum: 18.5 Mkeys/s

    Leopard (10.5.4?)
  • Reduced: 8.2 Mkeys/s
  • Automatic: 17.3 Mkeys/s
  • Maximum:15.8 Mkeys/s

There might have been another process in the background on the last maximum value.

Third, it kernel panics. On transitioning from idle to full load. On Tiger and on Leopard. It doesn't with the power set to reduced, but that's not the point of having a quad, or is it? You can get it running by switching to reduced power mode, putting full load on the system, and then switching to maximum. Once it runs, it runs for days, so I don't think that the cooling system is broken. It doesn't leak, either.

I can think of two reasons, first, the SMU doesn't accelerate the fans fast enough to cope with the rising temperature in the CPU, second, the cooling system for whatever reason might be just capable of cooling the machine in a stationary state, but fail under the special condition of going from idle to full load. I still have AppleCare until 2010, but I need the system right now and will have to take care of it myself for the moment.
Perhaps you or your readers have better ideas and/or experience?
Kind regards, Hendrik M."

Rushed here but a couple questions:

  • Have you looked inside of any signs of a coolant leak?
  • Are you using a UPS? (if so what rating, and do you have any way to check the line voltage on your AC outlet)
  • Did you check the Pwr Supply connections (see bold notes above)

Added this report here and on the PowerMac G5 Coolant Leaks page also - as the replacement parts mentioned sounds like there was a leak, although the absorber mat may have masked that from his initial inspection.)

(added 4/7/2008)
"I purchased a Power Mac G5 Quad (2.5 Ghz with the Delphi LCS) back in December of 2005 along with an AppleCare warranty. (So it's still under warranty then?) Not sure if I had a leak, but CPU Temps on Processor B were consistently a lot higher than processor A by on average 50celsius (this started around November 2007). I usually use this machine for Aperture, Adobe PS, and also as my World of Warcraft machine. About a month later (December 2007) I started experiencing random forced sleeps (sleep or shutdown?) along with a red LED visible from the front whenever playing WoW or using Photoshop. I opened the box up and checked for leakage or signs thereof and wasn't able to find anything.

I brought my Power Mac into the Apple Store after making an appointment in early January and after a preliminary check (and my showing them excerpts from my system log showing thermal runaway and stats) (system log entries on "PMU forced shutdown, cause = -122" and/or "thermal runaway" messages were also noted by others here.-M) was told that a new Logic board, power supply, cooling unit, and processors needed to be ordered. (sounds like there was a leak if all those components needed replacing) The store quoted me a turnaround time a 7-10 business days to allow shipping time for the parts and to test the system. A month went by and I hadn't heard from the store (Thank GOD for my MacBook Pro), so I contacted AppleCare to get a status check on my repairs and was told that the part that they were waiting on needed to shipped from Washington and was being overnighted to the store that afternoon. The store contacted me the next day and left a voicemail on my phone requesting that I call them back. Long story short, they replaced my G5 Quad with a brand spanking new (Mac Pro) 3.2GHz Octo 8800 GT. :-) that put a HUGE smile on my face, needless to say!
Yeeehaw for Apple. Now I know why I have been and always will be a Loyal, Apple Fan!

I'm impressed that they've replaced some out-of-warranty coolant leaking systems (and giving higher optioned Mac Pros than base for those that had higher end G5 towers apparently), although some didn't get a no-cost system swap, more than a few have especially over the last 6 months. (One recent report noted he had to pay the est. repair costs to get the new system, but some were offered new systems at no cost.) In some cases in the past, not giving up on the first response (pressing for a replacement/repair at no cost) resulted in getting a new system replacement. (ref: reports on the page on PowerMac G5 Coolant Leaks.)

(added 3/10/2008 - updated 3/12/2008 w/Serial Nos.)
"We had this problem on two separate Mac Dual 2.5Ghz G5 towers that we bought here at work when that model was new, about 3+ years ago. It turned out to be bad thermal sensors on the processor modules, which would report too high a temp., causing the system to shut down. Once we figured out the problem (with the help of some internet posts) Apple replaced the processor modules under warranty (the Macs were only a couple of months old)

The proof was repeated "thermal shutdown" entries in the system log. Once we knew that, as a test we could provoke a shutdown by running a bunch of Photoshop actions which would exercise the processors until shutdown (usually only took a minute or two) -- then check the system log to confirm.

This was a specific problem related to initial production batches of those Macs, but I thought I would mention it because it produced the symptoms being discussed here. After the fix, everything has worked well since without further incidents.
(I asked him for his S/N just as a FYI)
The two 2.5G Dual G5 Macs we had were:

  • Serial No.: G84365XNQPS (new Sept. 2004) and
  • Serial No.: G84501WVQPS (new Dec. 2004)
    -Mike S."
  • An old post from back in 2006 here also mentions a Thermal control bug affecting some LCS macs - referring to a thread from Dec. 19 2005 on g5 thermal overtemp bug (patchwork.ozlabs.org/linuxppc64/patch?id=3765P. Back then a some users also reported the problem due to ext. power sources (two were UPS related and another had a link to an article on the problem (also noting the fairly common "PMU forced shutdown, cause = -122" or "AppleSMU -- shutdown cause = -122" in the system logs) at www.gibbilicious.com/gibbilicious/2005/10/_mac_g5_desktop_spontaneously_1.html.

    (added 3/10/2008)
    " I reported to you some time ago about my random shutdown problems on a PowerMac G5/2.3GHz and my solution - namely, using reduced power mode. This has worked for me for over a year. I took a printout of the system log to an Apple Store for review by an Apple Genius and they gave me an estimate of about $1700.00 to replace the motherboard/processors. I ended up foregoing the repair. I have followed the travails of others with this problem and have tried each and every "solution," with no success. At my wits end, I finally broke down and bought a new MacPro (due today). This situation is so frustrating since it seems to be fairly common and reproducible. I wish Apple would recognize the problem and offer some remedy, but I don't see that happening. Thanks for the great site.
    -Mike F."

    (added 3/7/2008 - updated comments 3/8)
    "I have a dual 1,8ghz G5 ( 8 ram slot), that I brought as a refub maybe 3 yrs ago. I had the random shutdown problem from day one but with no Applecare I never pursued the problem with Apple. I tried all the tricks but found that only running in Reduced (Performance) mode helped. I've run in that mode for the last 2 yrs without a single shut down.
    Actually since upgrading to Leopard, I've run on Automatic without a problem. I saw the recent post about toggling the Energy performance setting and tried running in Hightest. My temperature monitoring program showed no difference in temperature. All was good for about 36 hrs when the shutdown struck. Nothing helped including cloning my firewire backup to the G5. I could not get past the gray apple screen trying to boot. I even had problems starting up from my install disk. Only a clean install of the HD and migrating my old files back has cured the problem.
    (Just for the record are you running an UPS? PS connections tight?)
    I am not using a UPS with my G5. The Power Supply connectors on the mother board appear to be firmly in place. Firm enough for me not to try and reseat them for fear of breaking something. All it took this time was one shutdown and I could not boot past the gray Apple screen. And that was also with trying to boot from another partition on the same HD and from my install disk. It would boot after several OF resets or selecting the startup disk after holding the option key on startup. I tried all the tricks, trashing PMU preferences, reset PMU button, reset memory chips, unplug overnight, nothing! On one successful boot with the install disk, it did not even recognize the hard drive. Was this from something corrupted in the boot process that cannot be repaired and requiring the OS re-install ? Thanks for your response. I've been following your page for many years now and have been helped many times from the old forum.
    Thanks again, Michael S."

    (added 3/3/2008)
    "My dual 1.8GHz G5 suffers from the same shutdown problem. Using the slick (and free) Temperature Monitor program I've been able to prove to myself that the random shutdowns are CPU temperature related.

    As suggested by other readers I tried running at the 'Reduced' Power Saver setting, and experienced zero such shutdowns. I also experienced much slower processing, of course.

    Today, in frustration, I chose the 'Highest' processor performance option to finish a Photoshop job, intending to revert to the low setting . . . but the processor temperatures plummeted to the lowest I've ever seen as shown by the rightmost part of this trace produced by the Temp. Mon. program. (The left part of the graph is typical for a no-load job environment in a 75 degree room. Anything over 135° on CPU A and I could rely on a shutdown within a few minutes. The rapid drop at the left part of the trace occurred when I first tried the Highest setting, the two interruptions occurred when I installed an update of the program.)

    temp graph

    Makes no sense, but it works for me!
    -Tom H."

    Toggling ES Performance settings (reducing, then going back to Highest) helped in the past with high fan speeds in G5 towers after some OS updates. Oddly just toggling the ES Performance setting and going back to Highest Performance sometimes solved this problem - I remember posting that tip many years ago in the news page after it helped in some cases. (FYI - a later report above said this didn't solve the problem.)

    (added 2/18/2008)
    "Have a dual 2.7 g5, am having the same problem, cpu crash, no reboot, no visible coolant leakage, took to the mac shop. Ran fine sitting for 36 hours. Brought it home, booted up, froze, will not restart... Very frustrating especially with the fact my 17in powerbook g4 laptop has had the screen replaced and the motherboard due to the vertical lines in screen, and the same week the screen lines came back, took it it in again (third time) for a new screen (apple care thank god) but no warranty on my g5 tower. These are used in my daily business (along with 9 other macs). Apple seems to be losing its touch for customer service and relations that it had before it grew (ipod....)
    Any news on "recalls" or apple actually responding in a way that is satisfying to its dedicated customers?
    Regards, Tom"

    Not that I have seen (but not checked apple's support/G5 section lately). Have you checked the Power Supply connectors? (just curious as noted above - a couple owners said that helped) - and a common workaround mentioned here before is setting Energy Saver Performance Option to "Reduced". (although you shouldn't need to do that - several owners have said it helped, including the most recent previous post below.)

    (added 1/16/2008)
    "My father in-law upgraded to the new Pro Mac, so I inherited his "old" PowerMac G5 DP 2.3. I know, I'm spoiled. Anyway, he was experiencing the random shutdowns, so he took it in to the local dealer to have it checked out before giving it to me. They could not find anything wrong with it (that is what my father in-law said, but I don't know what was actually checked). It is still experiencing the shutdowns, with the "PMU forced shutdown, cause = -122" being reported in the system log. I have reset the PMU and taken out all but the factory installed memory (512mb from the factory, but has a total of 4.5gb), but still have the shutdowns. I sort of rule out power problems outside the computer since my father in-law was having the same problems at his house in another town, but it could be. I have run it with and without my UPS.
    Some have mentioned iTunes and QuickTime as instigators. For me, it is running Flash. My daughter plays some Flash games on Disney's website, but anytime she tries it on the G5, it will shutdown. I am going to run the hardware check from the install disk tonight, but I don't have a high level of confidence anything will be found. (Although rare I think, also check the Pwr Supply connections - see note above) It is no longer under warranty, so any hardware fixes will be hard to stomach. I will also try running in Reduced mode. If that fixes it, it will be better than having a random shutdown during a long bit of video processing.
    (he later wrote)
    As others have discovered, running the CPU(s) in Reduced mode "fixed" my problems. It certainly isn't the desired fix, but at least the thing isn't randomly shutting down anymore.
    -Edwin F.
    Software Engineer - iSTARS
    Space & Geospatial Intelligence BU"

    (added 7/9/2007)
    "G5 Quad 2.5 4.5GB Ram - Maxtor Sata1 500GB Hd.
    About 1 month ago my machine started to shut down, and the LED number 7 on the Motherboard would light up. I reset all the Usual suspects ( PRAM, NVRAM, FIRMWARE,SMU etc ) to no evail...

    I did notice that It followed a definitive pattern... Randon shutdown followed by a complete failure to restart for approx 3 attempts, when on the fourth attempt it would fire up. I the removed all extra RAM, Harddrives, external Components, plugged it directly into the mains ( no surge protector etc ), it still failed.

    The machine is 14 months old, and guess what, no applecare. Sent it in to have it repaired, It was diagnosed as having a bad CPU . The whole CPU module was replaces at a cost of 1625Sf ( swiss Franks ). Got home plugged it in, within 15 mins it failed again.

    This time I had some crash Logs, and, although the PMU did not report any issues, (FYI - the "PMU forced shutdown, cause = -122" log entries in /var/log/system.log was often seen by others with random shutdown problems) the crash log indicated the CPU ( any of them ) getting a deadlock signal, and panicking. It also reported I/O failures too.

    I did some more investigation and came across the apple report on the failure of PSU's in certain G5 towers. (FYI - mentioned here back on Nov. 6th, 2006) Low and behold my quad fell right into the serial range. Also it states that if you have been charged for a repair that later ends up being related to the failure of the PSU Apple is liable to refund you your original repair costs....

    So I sent the Mac back with a printout of all the crashlogs, a printout of the Apple Info page about failing PSU's, and a video of it failing again( shows LED 7 lighting up like a christmas tree, and the mac failing to boot past the boot grey screen.). They cant argue with all that can they!
    Still waiting to here back from them.
    (he later wrote)
    I have been talking to a chap who works for a certified Apple repair shop in California, and apparently Apple is also replacing Motherboards based on the same issues as the PSU's ( bad capacitors ) This is NOT noted on the website. Its one of those things that you need to find out the hard way, and it still only applies to the models in the serial range that is on Apples website...
    They will replace them outside warrantee if the issue is deemed to be related.
    -Gordon (Switzerland) "

    Although not a G5 Tower owner, a QS owner wrote he's also had random shutdowns (with the infamous "PMU forced shutdown, cause = -122" log entries in /var/log/system.log):

    (added 7/9/2007)
    "I have a QuickSilver PowerMac that used to do this a LOT. I tried everything, a new PSU. Still shutdown. Etc. etc.When I bought a dual G4 1.8 processor upgrade for the card, same thing.

    Then, I decided to keep the case cracked open a little. It is about an inch open at the top. It's gone. I haven't seen a PMU -122 error in......I can't remember. I think it is a heat issue, the inside of the case is getting too hot, and the PMU is sensing the CPU is too hot, and shuts everything down.

    Anyhow, that is what cured my problem. Keeping the case a little open to let the hot air get out.
    -Eric D."

    I'd also check to verify the large internal fan is working and check for dust buildup. Although opening the side cover on G4 towers has been used in the past by some (including using a large house fan to blow over the logic board/CPU) as a test to see if problems (KP's, etc.) were due to overheating), the G5 tower's side cover removed won't really help IMHO as there also a plastic shield/cover inside and if that's removed the fans default to 'fail-safe' full speed mode, at least on G5s like my 2003 model. Although some posts here noted some dust buildup cleaning didn't solve the random shutdown problem, it has been a cause of overheating in the past (several readers have mentioned cleaning/blowing out dust in heatsinks, around the logic board, fans, etc. as helping with overheating problems on CPU upgrades, G4 towers, etc. and a G5 owned noted cooler running after a 'spring cleaning'.

    (added 7/6/2007)
    "Yes I am having the same issue - I have a G5 2.5GHz tower and I am experiencing random shutdowns especially in hot weather. Nothing else is wrong except when it acts up I can not use it. I am on my laptop today due to this issue.

    I have reset everything and tried to trash the power management plst and network plst and nothing.

    I will probably need to take this in to repair it. I will replace the battery on the motherboard first and see if that helps. So far nothing...
    -Susan "

    I tried to write Susan but the earthlink anti-spam page doesn't show the image you have to ID to get the mail to go through (and the audio option could not be heard in safari or FFox here - tried 3 times on each). I was going to ask her if she has the "PMU forced shutdown, cause = -122" log entries (in /var/log/system.log), if her AC power has been stable (no sags or dropouts) and if liquid cooled to check inside for any coolant leaks. (She mentioned it was worse in hot weather - so check for coolant leaks if liquid cooled, also check for extreme dust buildup, which has been a cause of thermal/overheating problems in the past even with other Macs.) -Some- affected owners that had expired warranties have mentioned using Energy Saver's "Reduced" Performance setting option as a workaround, but I'd not be happy with having to resort to that even if it did solve it.

    FYI - Apple Doc on Xserve "Unexpected Reboots": (5/29/2007) Apple posted a support doc titled Xserve: Unexpected reboot causes (doc no longer online) which also mentioned the -122 log entries (in /var/log/system.log) that G5 tower owners with the 'random shutdown' problem have often seen ("PMU forced shutdown, cause = -122"):

      If you receive a -122 shutdown value, you should take the following steps:
      1 Verify power source:
      Typically, the -122 entry is present if an Xserve experiences a complete power loss or a fluctuation in power supply that requires the Xserve the shut down. If your Xserve shuts down as a result of a power-related issue, it is recommended that you investigate the power source for reliability.
      2.) Verify hardware integrity. (run Apple hardware test)

    Another report on using "Reduced" performance setting as a workaround.

    (added 2/27/2007)
    "I have been following several threads on the web (including yours) regarding the random shutdowns on G5s. I, too, have been experiencing the random shutdowns on my 2005 G5/2.3GHz (air-cooled, not liquid cooled) which are always accompanied by the "PMU forced shutdown, cause = -122" entry in the console log. I used to reliably produce a shutdown when I either started iTunes or plugged in an iPod (which would then boot iTunes), but only if my Energy Saver settings were set at either the Automatic or Highest processor setting. When at Reduced, I never get the random shutdown. (Two earlier reports also mentioned running "Reduced" performance setting helped, although you shouldn't have to. (But for those out of warranty or just tired of trying to get it repaired, I can understand).-M)

    At the Automatic or Highest setting, I would typically have at least one, often more, random shutdowns per day. Often the shutdowns occurred at night when the only thing running would be the Unix maintenance scripts. I switched to the Reduced setting 8 days ago and have not had a single shutdown. I have tried reinstalling OS X 10.4.8, reseating my memory (6GB) and blowing out all the dust bunnys inside the G5. No luck.
    Interestingly, when I tried reseating the memory, I was really having a problem with iTunes causing the shutdowns, so I started with only the Apple-supplied memory and added the memory back after each successful test with iTunes. I was able to get all the memory installed without any additional shutdowns resulting from starting iTunes. I felt I had found the problem, but the random shutdown (unrelated to iTunes) continued.

    The interesting thing about my random shutdowns (at least for the ones I have witnessed) is that the fans do not spin up any more than normal prior to the shutdown. The machine just shuts down (or restarts in my case since I have it set to automatically reboot on power failure).

    The G5 is out of Apple warranty, although I purchased the computer on my American Express card and they double the manufacturer's warranty. I have been authorized to take the computer in for diagnosis, although I'm afraid it will take Apple weeks to troubleshoot the problem. Since it is running fine in reduced mode, I'm going to wait until I can be without the computer for several weeks before I take it in. I wish Apple would recognize this problem and come up with a solution.
    -William "

    (added 2/27/2007)
    "Yeah, I had this too on my PowerMac G5 2x2.5(Feb 2005). Fans would spin up with great hum or it would shut down on occasion to the point I couldn't even boot it at all (Jan 5, 2007). End up being a coolant leak that rendered entire system unusable. Luckily I had a Apple Care (purchased it with a system Feb 2005), so Apple decided to repair it, but even after a two House Calls and two complete swaps of Logic Board, Power Supply and CPU with a Cooling System no luck, it wouldn't even start.
    Then Apple decided to replace entire unit with a new Mac Pro. Now that was another unpleasant episode of dealing with Apple. It certainly isn't the Apple we used to know.
    It took almost 4 weeks to get the new Mac Pro. The Customer Service was rude, unknowledgeable and indifferent. I don't want to go into details, but by far, the worst experience I had with Apple in 19 years.
    What some posts are failing to realize is that CPU replacement includes the Cooling System, it is an integral part of the CPU, and most, if not all, thermal issues are due to failing or faulty Cooling System. (Checking for cooling leaks is certainly something to do if you have a Liquid Cooled G5, but some have had random shutdowns on air cooled G5s also. I've had several readers report cooling system leaks in the past, but to be honest I don't recall them mentioning random shutdowns in those mails, however some did mention seeing higher CPU temperatures reported which is why they went looking for causes and saw the leak. (And higher temperatures could cause a thermal shutdown)-M)
    Power Supply in this systems sits right bellow CPU/Cooling System so the smallest drop could cause the shutdown or even worse.
    (No leak is good (it should be repaired), but it would take more than a drop of coolant on the PS top case surface to cause a PS problem, but if enough seeped into the PS it could cause a short circuit if the liquid bridged some areas of the PS. But if it leaked enough to drip into the power supply, the system would likely have already been overheating (and shutting down) before enough fluid leaked out to flow enough into the PS internals to short it out. (If that happened the system would never power up again with that PS.)-M)
    Someone mentioned that most problems with this systems occur around 20 -24 months of use, so could it be design flaw????
    -DM "

    Some saw this long before years of use (see report yesterday, noted seeing it "Within a week" of a new system purchase). There have been some revisions to the cooling system (some had dual pumps, some single IIRC and at least 2 different mfrs). Regardless checking for a coolant leak is certainly something to do if you have a Liquid Cooled G5 and it's shutting down from overtemp (i.e. Log shows thermal shutdown) or you notice it's running excessively hot. For those that reported random shutdowns with a liquid cooled G5 and didn't mention a leak, please check for that first.

    (added 2/26/2007)
    "Within a week of purchasing my G5 dual (2.3GHz) (bought new, not refurb), I started having the random shutdowns. I could easily reproduce the event by launching ITunes. It got so bad that I still flinch when launching it, and don't really like ITunes because mentally I associate launching ITunes with a forced shutdown. The shutdowns were entirely random (other than the guaranteed shutdown with ITunes). Could be running Photoshop and move my mouse, or surfing the web and it would just shut down as if someone pulled the plug.
    (just curious - did the logs show a "PMU forced shutdown, cause = -122"?)

    Apple Support ran me through all kinds of steps before finally saying I needed to take it in for servicing. They replaced the power supply, and extended my warranty on this one problem for 90 days. The power supply seemed to fix the issue...until today. I'd just gotten to the point that I wasn't always flinching when opening Photoshop and other apps, and just as I let my guard down, it's started again. I've had four shutdowns in 15 minutes.

    I guess next I'll have to have the logic board replaced, if they do honor the extension. If not, then it's my first bad Apple.

    It hasn't happened now for nearly an hour, so I'm praying it was just a freak thing instead of the issue being back. It's really frustrating. On the one hand, I'm aggravated at Apple because they yanked me around for so long. On the other, I have to say I appreciate that they said they'd make sure it's fixed (if it's within the 90 days). I got yanked around with that too and had to fuss for it.

    It's obviously an ongoing problem with the G5s. I don't know if Apple is ignoring it or truly clueless about it. But it's been very disappointing.
    -Juli L."

    (added 1/30/2007)
    "I've been having this problem more and more often lately (G5, dual 2Ghz). After reading all the possible fixes on your site, I went with the path of least resistance and tried the easiest sounding fix - setting my Energy Saver CPU performance level to "Reduced." I've not had another shutdown since. I've been good for more than a week with some heavy duty usage nearly every day. Hopefully it will stay fixed.
    Thanks, Scott "

    Another earlier report mentioned that solved it, but you really shoudn't be forced to run in that mode. (Although with no warranty left I understand...)

    (added 1/30/2007)
    "I just thought that I would comment on the random shutdown problems. I have a PowerMac G5 Dual 2.7 system which I purchased in March 2005. Within the first week, I was having the random shutdown/reset issues. I took it to the Apple Store and they ran a battery of tests which found no problems.

    I did more investigations online and found that other people were seeing this problem and that they recommended looking for thermal runaway problems in the logs, which I did. "Luckily," I saw this issue and made a copy of the log. Instead of going to the Apple Store, I called Apple Care. Despite having to make an extra effort, a technician was sent to my house and they replaced the processors and heat sink. From that point until about 4 months ago, my computer worked great (despite the fans always making random noise).

    So, 4 months ago, I started seeing the problems again. I did another look at the logs and found the same problem....

    Dec 23 09:56:32 jc-lewis-power-mac-g5 configd[37]: posting notification com.apple.system.config.network_change
    Dec 23 09:56:32 jc-lewis-power-mac-g5 lookupd[4390]: lookupd (version 369.5) starting - Sat Dec 23 09:56:32 2006
    Dec 23 09:56:33 jc-lewis-power-mac-g5 mDNSResponder: 13967: Client application registered 2 identical instances of service iTunes_Ctrl_31EF68AD06914428._dacp._tcp.local. port 3689.
    Dec 23 09:56:35 jc-lewis-power-mac-g5 configd[37]: AppleTalk startup complete
    Dec 23 10:00:04 jc-lewis-power-mac-g5 kernel[0]: PowerMac7,3 Thermal Manager: Thermal Runaway Detected: System Will Sleep
    Dec 23 10:00:04 jc-lewis-power-mac-g5 kernel[0]: PM73 T_cur=110 >= (T_max:88 + sleepOffset:20)
    Dec 23 10:00:04 jc-lewis-power-mac-g5 kernel[0]:
    PowerMac7_2_PlatformPlugin core dump:
    Dec 23 10:00:04 jc-lewis-power-mac-g5 kernel[0]: IOHWControls:

    I called Apple Care again about a month ago. According to Apple, they have root caused this problem since my previous house visit. Their recommended course of action is to replace the logic board (I didn't get a reason why). I expect to be getting a house visit in the next day or so. If you like, I can let you know the result. I hope that this information is helpful to you and to others. Personally, my history with Apple has been great thus far with several products and I'm not deterred by a hardware bug that was in their newer technology (I'm an engineer so I can relate). I would hope that an issue like this doesn't affect other customers in a negative way. I hope that people seeing this issue can have enough information to explain it to Apple technicians so that it can be fixed for them.

    Another good resource that I've found is www.g5support.com. It has lots of helpful information on all kinds of topics. I hope it gets resolved soon. Good luck with your friend's issue.
    Regards, JC "

    BTW - I've had some G5 tower owners say after service (CPU/logic board swap, etc.) that their system fans ran at high speed. I assumed apple ran a thermal recalibration after the service (done after a CPU replacement for instance). I asked if toggling Energy Saver performance settings helped (old tip from the past after some OS X updates.) One reader w/replaced PS said the fans were much noisier than before - even when not running at full blast.

    (added 1/3/2007)
    "I've been having some issues over a year now with my Mac G5 1.8Ghz Late 2004 (The one that the memory can only be maxed to 4 gigs). What's been happening is that when I run my music software or any software that raises the temperature on the computer it goes into a sleep mode. I installed that free temperature program everyone uses and when I first turn on the MAC it states that my processor is 58 degrees but as soon as I run a program it jumps to about 64, 68, 74.4 and then that's when it goes off.

    I work on PC's alot at work. When I see issues like this, the first thing I think of is the heatsink. I took out the logic board, power supply and cleaned everything with a dust can. I even took off the heatsink and put a little bit more of that heatsink silver paste onto the processor which did cool my CPU to the new 58 degrees before it was 60 something can't remember.

    I took out the power supply and saw all the nasty dust on the fans and I remember always hearing that nasty noise that fans make when they sound like they're dying. So I bought new 60mm good fans for the power supply. Sounds so much quieter now.

    Cleaned the entire case and put everything back in it's place. I even customized a new dual cooling fan to be place in front of the plastic that sits on the heatsink to have extra air blowing in front since the back is getting air. I noticed dual macs already have fans like that in their machines but not mines.

    After all is said and done with a new clean, dust free Mac, it shut down on me again when running my music software.

    Here's is the Console Log where it states the problem and I searched for the keyword everywhere on the internet and no hits whatsoever.

    So I'm wondering, do I need a new logic board, new power supply? My warranty is over and I can get the Applecare but standing in these longs lines at the Apple Store is daunting. What do you think?

    Feb 21 02:27:05 music-studios-power-mac-g5 kernel[0]: IOSMUPwrController:: OverTemp notification
    Feb 21 02:27:05 music-studios-power-mac-g5 kernel[0]: Power Management received emergency overtemp signal. Going to sleep.AirPort: Link DOWN (Client disAssoc 0)
    Feb 21 02:27:06 music-studios-power-mac-g5 launchd: Server df47 in bootstrap 1103 uid 0: "/usr/sbin/lookupd"[677]: exited abnormally: Hangup
    Feb 21 02:27:06 music-studios-power-mac-g5 configd[57]: posting notification com.apple.system.config.network_change
    Feb 21 02:27:20 music-studios-power-mac-g5 kernel[0]: System Sleep
    Feb 21 02:27:20 music-studios-power-mac-g5 kernel[0]: System Wake
    Feb 21 02:27:20 music-studios-power-mac-g5 kernel[0]: Wake event 0020
    Feb 21 02:27:20 music-studios-power-mac-g5 kernel[0]: FireWire (OHCI) Apple ID 52 built-in: handleSelfIDInt - received quads == 0. issuing bus reset
    Feb 21 02:27:20 music-studios-power-mac-g5 kernel[0]: Sound assertion "kIOAudioDeviceActive != getPowerState()" failed in "AppleOnboardAudio/AppleOnboardAudio.cpp" at line 6920 goto handler
    Feb 21 02:27:21 music-studios-power-mac-g5 kernel[0]: USB caused wake event (OHCI)

    The keyword in that log is:
    Feb 21 02:27:05 music-studios-power-mac-g5 kernel[0]: IOSMUPwrController:: OverTemp notification
    Feb 21 02:27:05 music-studios-power-mac-g5 kernel[0]: Power Management received emergency overtemp signal. Going to sleep.AirPort: Link DOWN (Client disAssoc 0)

    I move the mouse and it comes back up.

    Will the Apple Hardware Test (on system DVD) completely run? (if so what if any errors does it report in extended test?) The older AHT I had for my 2003 G5 doesn't do thermal monitoring apparently as the fans ramp up to failsafe mode (i.e. full blast).

    (added 1/3/2007 from Dec. 21st, 2006 mail)
    "This forum has been helpful to me, so thanks.
    The day before Thanksgiving 2006, my dual 2.5GHz G5, purchased early December 2004, started random shutdowns. I had noticed the fans intermittently revving for a couple of weeks prior to this, and I remember thinking that I should vacuum the computer innards. Before finally giving its last gasp and refusing to start, it began turning itself off after shorter and shorter periods. When I put it in my car to take to an Apple-authorized technician, I noticed green coolant had leaked onto the bottom metal plate. When he opened it, the technician felt it had been leaking coolant for some time, as there was dried gunk on the bottom of the processor unit, and the power supply was rusted.

    The information gleaned from this and other web sites on this G5 problem helped considerably in making a case for replacement of the processors, power supply and logic board. On December 1, after hanging on the phone for 2.5 hours, most of which was spent waiting for the next person up in the hierarchy, an Apple product specialist okayed the replacement. Hurray! The following week, my technician received the power supply and logic board.

    It is now December 22, three weeks after the initial replacement decision, and we are still waiting for the processors. Apparently supply and demand are not equal, and I am certainly not a high priority on the list. In a call last week to my product specialist, he indicated that the processors should be released within a couple of days. Twelve days later, still no sign of the processors, and the scheduled arrival date on my technician's order still says December 8. Four more calls to my product specialist this week have gone unanswered -- I can't blame him for not wanting to share bad news. On the other hand, any news would be better than none. My back is to the wall for work for which I need the G5.
    Has anyone else had to wait this long for their replacement processors? Any suggestions for how to get this moved up the ladder?
    Thanks, Elaine "

    I really don't know what would speed up the process if there's a availability problem at the source.

    (added 12/5/2006)
    "I bought a Power Mac G5 Dual 2.3GHz (*not* dual core), back in May of 2005. In MacTracker, this machine is referred to as a "Q87", or "Power Mac G5 (Early 2005)". I also bought a 23" Cinema Display. I purchased AppleCare on both.

    For the first few months, the machine seemed fine. Then, I started noticing that the machine would occassionally randomly shut down when I launched iTunes. There would be a corresponding entry in the system log mentioning that the PMU forced shutdown due to cause -122. (many that had the random shutdown problem mentioned that system log error - although not everyone checked for it.)

    I eventually determined that the sudden shutdowns when launching iTunes only occurred when the Energy Saver CPU performance setting was either Automatic or Highest. When set to Reduced, the machine would run fine. I've run in Reduced mode ever since, occassionally switching back to Automatic and Highest to see if the same issue would recur. It always did. I also discovered that rarely, launching other applications would cause the shutdown. iTunes would cause a random shutdown better than 95% of the time.

    Just a few weeks ago, I had some time to call AppleCare and get the issue resolved. I told the AppleCare rep on the phone that I had tried all the usual suspects: clean installs, reset PMU or SMU, reset NVRAM, etc. No dice. They gave me a case number to take the machine to the local Apple store for repair. According to the paperwork, Apple replaced the logic board and both CPUs.

    I've had the machine back for only two days, but so far it seems OK. I won't be completely convinced unless I can run the machine in Automatic or Highest with no random shutdowns for at least a month or two, though.
    (name withheld by request) "

    (added 12/5/2006)
    "I have had about 4-5 random shut downs in the last 6 months. (did the system log show the "PMU forced shutdown, cause = -122" error?) I did have my power supply replaced almost a year ago. However, I have noticed that my G5 tower (dual 2GHz) runs better with only 6GB of RAM vs. the 8GB I normally use. So I think this leads me to think the quote "machine will randomly try to draw more power when performing different tasks" maybe be accurate. (that was a comment from a reader below yesterday that had a defective Power Supply replaced) Logic has me believe 6 memory sticks uses less power than 8 sticks.
    (Yes, 8 dimms would use a bit more power than 6, but Apple should have designed the power supply to handle a fully loaded system (including PCI slots, drives, etc.) with some additional margin. (However faulty RAM can cause all sorts of problems - and as mentioned here before so can an under-capacity UPS - if using one test w/o it.) I have 8 dimms in my 2003 Dual 2GHz without any problems so far. (Running for years with six 512MB dimms and two 256MB dimms, although I did run tests for a couple weeks with up to eight 1GB dimms without any problems seen - see older article here on G5 RAM Tests - Photoshop/Multitasking performance w/512MB to 8GB of installed RAM.
    Chris later replied:
    I will check my system log for that entry. Hopefully it hasn't been cleared. I have tested several different manufacturers sticks of 1GB each to total 8 installed and I get the same results. Lastly after rereading your article, I may try running my machine without my APS battery/surge backup to see if I am being starved for power.
    Thanks for your reply and I will let you know what I find.
    -Chris "

    (added 12/4/2006)
    "I came across your page regarding G5 random shutdowns and thought I should share my experience with you.

    I have a 12 month old G5 Dual 2.5 GHz (June 2004 model) running OS X 10.3.9 which suffered the exact same symptoms. Interestingly it is NOT one of the models/serial numbers listed in the Apple Repair Extension Program, (see Nov 6, 2006 info below) and I notice most other posts are from people running OS X 10.4+ on different model G5's.

    The machine ran perfectly for about 6 months after purchase, then without warning it developed the random shutdown problem. Initially it would happen perhaps once a week or so, and would occur whilst performing different tasks and while running different programs (Mail, Photoshop etc.). There seemed to be no pattern to the shutdowns at all, and I was always able to power up afterwards without any problems.
    At the time I put it down to fluctuating power in our home, however when it started to happen more frequently I realised there was a problem with the Mac itself. As the shutdowns were inconsistent, and I had not recently added or upgraded any software, I suspected faulty hardware was to blame. (Did you check the system logs to see if there was a related entry? like the commonly reported "PMU forced shutdown, cause = -122".)
    I performed an extensive hardware test which reported no errors whatsoever. The shutdowns continued, and then the Mac started refusing to power up again afterwards. Sometimes it would get as far as the grey apple screen and then shut down, sometimes it would power up for only 3-5 seconds and shut down (it would do this repeatedly), and at other times I would get absolutely no response from the power button. (That sounds like a more severe problem than the random shutdowns most others reported - more like a power supply failure.)
    If it refused to restart at all, I would leave it overnight and then it would restart - until the next random shutdown. After a lengthy phone call to Apple support, who had me go through all the obvious steps (most of which I had already tried myself) they referred me to a local Apple dealership for repair. The technician there diagnosed a faulty power supply over the phone, which was a lot more than Apple support had done. The Mac was picked up, repaired and returned to me with a new power supply, and so far (2 months) there has been no recurrence of the problem. The technician told me it is a common fault, and that the machine will randomly try to draw more power when performing different tasks (even rebooting) and if it can't do so then it will simply shut down.

    So, I would say to anyone with the same symptoms, don't waste your time reinstalling different versions of OS X or phoning the Apple support hotline. Speak to a technician at your local Apple dealership and get your Mac's hardware repaired - hopefully you will be covered either by your warranty or by the Apple Repair Extension Program. (see info/link below) If not then I would keep pursuing Apple until they reimburse you for the repair, after all it is not an isolated issue.
    Hope this helps.
    Regards, Sarah B. "

    Some readers that had their towers serviced mentioned repairs ranged from Pwr Supply and Logic board (plus ram) replacement to just a graphics card in one case.

    PowerMac G5 Pwr Supply Repair Extension Program: (posting as a FYI - although the Apple doc does not mention random shutdowns as qualifying)

    (added 11/6/2006)
    "Just thought I'd drop you a note because this might be related...
    Apple has just issued a repair extension program for power supplies on certain G5 Powermacs. Interestingly, my serial number does NOT fall within the range. But, if the problems being posted here really are due to the power supply, I would expect this extension program to expand. (Apple's "Power Mac G5 Repair Extension Program for Power Supply Issues" - expired now, originally at www.apple.com/support/powermac/powersupply/repairextension/ )
    -Brian B. "

    For those readers that mentioned their systems were repaired previously, some had PS+Logic board (and sometimes even RAM) replaced, although one reader said they just replaced his video card. The Apple doc does not mention random shutdowns (refers to power up problems), but regardless definitely check to see if your G5 Tower falls in the serial number range listed:

    "The Power Mac G5 Repair Extension Program for Power Supply Issues applies to Power Mac G5 systems that have power-related issues as a result of a specific component failure within the computer's power supply. If your Power Mac G5 fails to start up after the power button has been pressed and your computer's serial number is within the noted ranges, your computer may be eligible for repair, free of charge. There are no known safety issues caused by this component failure.

    Identifying Affected Power Mac G5 systems
    The affected Power Mac G5 models were sold between approximately October 2005 and August 2006 and feature Dual 2GHz, Dual 2.3GHz or Quad 2.5GHz PowerPC G5 processors.

    If Apple or an Apple Authorized Service Provider (AASP) determines that your Power Mac G5 computer is eligible as part of the program, the power supply repair will be covered by Apple for up to two years from the original date of purchase even if your Power Mac G5 is out of warranty. This worldwide Apple program does not extend the standard warranty coverage of the Power Mac G5.

    Affected systems will exhibit one of the following power-related symptoms:
    * System will not start up after the power button is pressed
    * No LED activity

    Note: If your Power Mac G5 is not experiencing any of these symptoms, you do not have to contact Apple or any Apple Authorized Service Provider.

    The affected Power Mac G5 computers have serial numbers where the first 5 digits fall into the ranges noted below. The Power Mac G5 computer's serial number is located inside the case directly below the air deflector, along with other configuration information.
    Serial Number Ranges
    CK539xxxxxx - CK608xxxxxx
    G8539xxxxxx - G8608xxxxxx
    YM539xxxxxx - YM608xxxxxx
    RM539xxxxxx - RM608xxxxxx"

    (added 11/5/2006)
    "Just writing to say I am having the same exact problem on my dual 2.3 G5, happened both on 10.4.7 and now 10.4.8. I can't remember when I upgraded to 10.4.7, so I can't say if that's when the problems started. I have done all the basics- hardware test, reseat RAM, reset SMU, unplug, check the power cords, etc... This simply HAS to be a software problem, doesn't it? I mean, if crashes are based on OS version? (although several recent posts here mentioned reverting to pre-10.4.7 OS version helped, older reports noted they saw the problem even with older (pre-10.4.7) versions.) I don't know, but I am very perplexed. I can reproduce the problem quite regularly buy launching multiple Quicktime files and giving it a minute to kill itself, or by running iTunes with Quicktime (s) simultaneously. Seems very much QT related in some way.
    Seems like a lot of 2.3 G5 Powermacs. At what point does this become something I can complain about even if I'm out of warrantee?
    -Brian B. "

    It can't hurt to try (especially if you ever reported it while it was under warranty). Odd you only see it with QT? Have you tried booting from another drive (with a clean OS install - not a clone of the current boot drive)

    (added 10/23/2006)
    "I wrote in about the random shutdown problem on Oct. 12. (below)
    Since that time, I called Apple yet again (about the fifth time) and talked to another PowerMac specialist. After reading over the symptoms, the product specialist immediately came to the conclusion that it was a hardware issue. They sent out a new power supply, a new logic board, and new RAM to replace the original 512MB.

    A technician came to my house yesterday and replaced all three components. So far (over the last 24 hours), I have not had any random shutdowns (knock on wood). I'm not sure if the issue was the logic board or the power supply, but it seems to be working like a champ now. By the way, I also saw the increased frequency of shutdowns after upgrading to 10.4.7 and 10.4.8 (currently running 10.4.8).

    This is a hardware problem. All I can recommend is to keep bugging Apple Support until you talk to the right person and they are willing to replace the hardware.
    -Brooks C."

    Definitely worth pressing (especially if under warranty or if you reported it to apple during warranty) as not everyone had this problem and you shouldn't have to revert to an older OS to solve it (which several mentioned recently reverting to 10.4.6 or 10.4.5 helped, although in the past some had the problem even with older OS's like 10.4.5).

    (added 10/17/2006)
    "Power Mac dual 2.3GHz, 2.5GB Ram
    I also, have had problems with intermittent shutdowns. I have been reading different forums for 3 weeks trying to find the right answers. I tried all the suggestions, including reset PMU, reseat ram, disconnecting devices etc. Then I came across this post on xlr8yourmac and have determined my problem solved by downgrading to OS X 10.4.5 from 10.4.8. I have been rendering video, listening to iTunes and downloading in the background for 3 days and no shutdowns.
    (He later wrote)
    I needed to upgrade back to 10.4.7 in order for final cut pro 5.1.2 to work (had a customers video project that needs to get finished) and sure enough back to random shutdowns.
    -Richard M."

    Another reader with the problem also said 10.4.6 worked. For some with the problem, it seems an OS earlier than 10.4.7 helped. (The first user to report on reverting to an older OS had updated from 10.4.5 to 10.4.7, then 10.4.8, both had the problem on his system so he reverted back to 10.4.5. A later report below said he was ok with 10.4.6, but not 10.4.7 or 10.4.8) The downside is that there are security updates in later OS versions. If the system is under warranty I'd try to get apple to service it.

    (added 10/12/2006)
    "I have been having the random shutdown problem on my 2.3 GHz G5 DP. After spending hours on the phone with Apple Support and taking my machine to an Apple Store, I still have not found a resolution. The latest suggestion from Apple Support is that it is a power supply problem in my home, but I don't buy that because I recently purchased a UPS that is capable of keeping the machine running. (what is the rating of the UPS?)

    The crash log only shows our old friend "PMU Forced Shutdown: -122".

    Some observations about my situation:

    1) The problem was very intermitant prior to the 10.4.7 update. After installing the update, however, the problem started occurring several times/day. At Apple's suggestion, I downgraded to 10.4.6. The problem went away. (One of the earlier reports said reverting to 10.4.5 helped. He had not updated to 10.4.6, instead going stright to 10.4.7 and later 10.4.8. I've not seen the problem here on a 2003 G5 tower in any OS X version, nor have many others but that's little consolation of course to those that have.)
    I did an "Erase and Install" and updated back to 10.4.7. The problem came back. I'm now running 10.4.8, and the problem is still occurring. It seems to me like a key to figuring out the problem would be knowing what changed from 10.4.6 to 10.4.7.

    2) After upgrading to 10.4.7 and updating iTunes, the crashes occur very frequently when launching iTunes. In fact, launching iTunes is about the closest I can get to reliably reproducing the error. Of course, it wouldn't shutdown at all when I had the machine at the Apple Store.

    3) In addition to the shutdowns when launching iTunes, the shutdowns also seem to be associated with mouse clicks. These occur much less frequently (and seemingly more randomly) than the iTunes shutdowns, though.

    4) The shutdowns seem less frequent the fewer external USB and Firewire devices that I have attached. The best case is only having the Apple keyboard and mouse attached, but the shutdowns still occur. I thought it might be a particular device or cable that was causing the problem, but after removing all devices and swapping out cables, it doesn't seem to be related to any particular device. Adding any device (printer, scanner, EyeTV, iPod, etc.) seems to increase the likelihood of a shutdown. I also have external USB and Firewire hubs, but both of these have their own external power supply, so I wouldn't expect any of the devices to draw much (any) power from the computer's USB or Firewire ports.

    5) The shutdowns do not appear to be related to CPU intensive tasks. I can run tasks that max out both CPUs overnight and have never had a single crash while doing so.

    6) I have done all of the usual things like resetting the PMU, resetting PRAM, etc. Nothing has helped. I've also run Apple Hardware Test and TechTool hardware tests. No hardware problems have shown up.
    -Brooks C."

    See Brooks' later report above (Oct. 23rd) where he had apple service the Tower.

    (added 10/6/2006)
    "Just noticed that you have updated the "G5 random shutdowns" page which reminded me of something I discovered with my DP 2Ghz G5 when it was having similar problems.
    Among the many things I tried to isolate the cause of these shutdowns (re-seat memory, re-seat all PCI cards etc. ) was to run the Apple Hardware Test - it is on every G5 install DVD (one of them). To use it, insert the appropriate DVD and boot holding down the Option key then select AHT.
    (Some users with the problem previously also ran the Hardware Test (mentioned here and here) but didn't see any problems reported. (And one reader mentioned a video card was replaced that seemed to solve the problem, another said it only happened after OS X updates, Some mentioned Pwr Supply replacements - there seemed to be no common cause. AHT often didn't report any problems, but it's always something to check with any error that may be hardware related.)

    Run a medium duration test first. This may take some time and the fans may ramp up, don't worry.

    My first test showed an error something like "Upper A" (I'm kicking myself that I didn't write down the exact error message) which meant that the Apple supplied 160 gig SATA I drive in the top drive bay had a fault that Disk Utility had not found.

    I replaced this drive with a new Maxtor SATA II 16mb buffer drive and the shutdowns ceased. SATA II does work fine with my DP 2Ghz G5 and is much faster than the Apple SATA I which is now repaired via Disk Warrior and living in an external USB 2.0 case. (G5s don't have SATA II (speed) interfaces so I'm assuming he means the Maxtor drive was just a better performer than the previous one. The drive just falls back to SATA I mode if the interface isn't SATA II. Some SATAII drives have jumpers to limit to SATA I in case there was some issue with an older interface, but often no jumper changes are needed. Although there have been some other issues with some drive brand/models and the onboard G5 SATA (some models of Seagates and WD drives for instance, mentioned in past news/drive db reports.))
    So AHT may reveal at least one of the causes. I hope this helps.
    Michael, JAPAN "

    Always worth checking on any error like that, but some have seen it and still had AHT show no errors.

    (added 10/5/2006)
    "I'm responding to your post on G5 tower random shutdowns. Here's my story:
    I'm using a dual 2.3 GHz G5, and it's been working flawlessly since I bought it about a year ago. A few weeks ago, I updated my OS from 10.4.5 to 10.4.7. As soon as I booted up after the install, I started having a maddening problem with my computer randomly shutting down. (Not sleeping, but a complete power down.)

    At first, the shutdown would happen immediately after powering up; my computer wouldn't even make it to the blue progress bar. I zapped the PRAM and did a hard PMU reset. Afterward, it would boot up, and I could log in, but the computer still shut down randomly.

    I checked the system console and found this (common) message:

      localhost kernel[0]: ApplePMU::PMU forced shutdown, cause = -122

    After several days of extreme frustration (and several hours on the phone with Apple tech support), the problem was still not solved. I did performed a re-install of 10.4.5, and all was well.

    Today I installed the 10.4.8 combo updater, and the same problem is happening. The feedback I've gotten from Apple and from macosx.com is that this is a hardware problem, but I don't buy that; it started happening immediately after the 10.4.7/10.4.8 patch updates, and if I revert back to 10.4.5, the problem ceases.
    I'm not using a UPS, just a regular surge protector. Also, I did try resetting the PMU, both by disconnecting the AC and by opening up the machine and pressing the internal reset button. Neither helped.
    (he later wrote)
    I did run Apple Hardware Test, and everything was normal. It certainly is odd.
    -Jeff A.
    Production Manager

    (added 7/22/2006)
    "I've had the same shutdown problem with my G5 Quad for quite a while. I've read all the comments across the web, and brought it in for repair, expecting a logic board or power source, as people frequently described.
    Instead, they told me it was a bad VIDEO board. Now replaced, my G5 (now on a UPS) has been working fine for a week so far...
    -Marcus M. "

    (added 6/15/2006, from 6/10 mail)
    G5 Tower Random Shutdowns
    I have had these random shutdowns now for the past several months on a G5 DP. The system log reports a "PMU forced shutdown, cause = -122". It is completely random and often frequent (3+ times per day). The G5 has run flawlessly for about a year since purchase. Now this. If it were something to do with the electrical supply why would this just all-of-a-sudden start happening? Apple really needs to address this. PMU resets have had no efffect.
    it's a dual processer 2ghz, so it's fan cooled. I am running the temp widget and the measurements are normal. it's been a serious problem but 2 days ago i removed all the ram and re-seated it and so far so good (!). i hope that is the issue but it seems a bit far-fetched. if it comes back i am thinking of replacing the ps but that will be a major hassle for sure. let me know if you have any suggestions!
    Jim H."

    (added 4/17/2006)
    "The friend I mentioned that has had PSU problems with his new G5 2.3 dual core now has a new power supply and it seems to be working. The repair shop he took it to said he has replaced 5 PSUs in dual core macs in the last 5 months, and that's the #2 repair shop in town. The #1 shop must have seen more.
    -Scott S."

    (added 3/24/2006)
    "I used to have the exact same problem on my 2nd generation dual 2.0Ghz G5 (seemingly random shutdowns). In my case it was pretty clear from looking at temperature readings and messages in the system log that something was up with my second CPU.
    After having it replaced it's been working like a charm for over a year. I suspect that the problem was a fault in that CPU's thermal unit.
    Regards, Johan P. "

    Although I had the Pwr Supply replaced (for noisy fan) early on in my 2003 (first batch) G5 dual 2GHz, knock on wood it's still running OK (never any shutdown problems) but some others were not so lucky (2 more reports added today)

    (added 3/24/2006)
    "Just thought I'd also let you know I have been experiencing random shutdowns on my PowerMac G5 too for the first time last week. However unlike most of your reports my model is not a dual core, its one of the original 2003 Dual 2Ghz models. I am running 10.4.5 with the stock radeon 9600 and 1.5GB of RAM. So far it has happened at random 3 times whilst playing World of Warcraft, although I don't think WoW is to blame.

    I bought the machine a week after launch and have never had any trouble other than that the graphics card died about a year ago (just outside of warranty) which I replaced with another 9600, as OWC were selling OEM ones for G5s at a very reasonable price.
    Cheers, Giovanni C. "

    (added 3/24/2006)
    "Thought I'd add my observations:
    I have an original dual 2 GHz G5 (stock, except for an extra 1GB RAM: 2x 512 MB DDR SDRAM PC3200U-30330, matched pair from OWC), had it for just over 2 years now. It has had problems since day 1, when it shut itself down in the middle of running through the initial setup. After that I saw no problems for over a month, but then I started getting random crashes around every month or so. These shut-downs are characterized by a sudden powder-down: screen goes blank, machine gets quiet, no fans running, but the light on the monitor and front of the computer stay lit for around 30 seconds - 1 minute. I did some searching in the logs but never found anything obvious. These shutdowns occur sometimes during heavy usage (playing WoW), and sometimes shortly after waking in the morning, doing light web-surfing and email.

    I have also had a few (probably unrelated) crashes of a different sort where screen goes blank and the fans kick into high gear and just keep getting louder till I force it to shutdown by holding down the power button for 15 seconds or so.
    (I asked if he'd tried some old tips like toggling Energy saver performance settings, reset NVRAM and resetting the PMU? (shut down, unplug AC cord for a few minutes))

    Finally, I have another problem that may or may not be related. I have an external firewire harddrive (oxford 911 chipset case, from OWC; with an apple stock 20GB HD from my wife's old 400MHzTiBook) that I use for backing up and transferring files. Whenever I plug it into the front firewire port on the G5 it blows out the entire "front panel" that is the firewire, usb, audio ports on the front of the computer. (Wow - that sounds like there's some sort of connector/wiring/short ckt problem. There's been some past reports on the G5 FW/USB reports page on the G5's FW ports blowing some FW Hubs that were not designed for FW bus voltages present, although they are still under the FW spec max. But that damaged the Hub, not the G5.) It seems to not have a problem when plugged into the back port, but I'm not sure about that. I can take this same drive and plug it into my wife's powerbooks (both the TiBook, and her new 1.67 GHz 15" AlBook) or the G5's at work and all have no problems with it.

    So what have I done? I have talked with apple about this extensively. They have been entirely unable to reproduce the random shut-downs, which is not surprising since they happen roughly once a month with daily use, though sometimes ill get 2-3 in a few day period. Thus I have gotten service based primarily from the blown front panel, which they have replaced twice, and the second time they also replaced the logic board. This has made no difference in the occurrence of the random shut-downs. I haven't tried to use the firewire drive since they last replaced the front panel, but i'm confident that it would again fry the front panel. I was using a UPS (I asked what the UPS rating was.), and I have tried not using it; using instead a standard surge protected powerstrip and even (shudder) plugging straight into the outlet! Neither seemed to have any effect on the occurrence of the random crashes.

    Surprisingly, the possibility of it being power supply related never came up in all my conversations with apple. I had thought of that as a possibility, but never got them to focus on it in trying to fix it. My current plan of action is to back up my machine (harder since I can't use my firewire drive!), then plug in the drive, fry the front panel, and take it in to get fixed. I'll demand they replace the power supply in addition to the front panel (and likely the logic board), and see if that solves all my problems. Thank goodness for apple care extended warranty! Always a good buy. Thanks for running such a great site! Keep up the good work!
    Cheers, Scott "

    (added 3/23/2006 from 3/17 mail)
    "Two DOA G5's in a row!
    #1 had the famous sudden shutdown problem. #2 had sleep issues.

    Both machines with the same specs- dual core 2.3 GHz, 4GB of Apple-installed RAM, (2) 500GB hard drives. Not connected to a UPS. No thermal issues noted in console log.

    First machine came Feb. 13, 06. First indications of trouble on the horizon came right out of the box. Following the User's Guide setup instructions to the letter, I plugged-in G5 #1, and it went ahead and booted-up all by itself, the second it got power from the outlet. (The electrical circuit has run other Macs successfully for years). The sudden shutdowns began five days after the initial boot-up.

    AppleCare ran me through all kinds of potential fixes. (And I've got to add that all the tech reps I spoke with were a pleasure to work with).

    Extended hardware test revealed no problems, ditto Repair Permissions/Disk Repair. But the shutdowns continued. Things got real bad when, upon attempting to restart the machine following a sudden shutdown, the power switch would "click" and the white power light would come on, but that was it, no boot-up. Persistent button-pressing would ultimately get it going again.

    A few shutdowns later, attempting to restart yielded not even a "click"- just the power indicator light, and silence from the G5. Dead in the water. Before Apple's 30 day cutoff point for doing so, I was able to present my case in such a fashion that the AppleCare product specialist could see that declaring the unit Dead on Arrival was the only rational path.

    Incidentally, the shutdown cause I kept getting in the console log was 122. Here's a link that explores that cause

    As for the replacement, which arrived Mar. 16, 06 ("Beware the day after the Ides of March," apparently): G5 #2 came out of the box and proceeded to freak the first time I put it to sleep. The 23" ACD (new in Jan. '06) started cycling between black screen and a featureless blue field, with the desktop pattern and dock thrown in, in quick flashes, just for variety, now and then. Hitting keys, clicking the mouse- nothing would stop this nonsense except holding down on the power button to shut the system down.

    AppleCare had me reset the PRAM, and ultimately do an erase and install of the OS. Neither did anything. The bad sleep behavior continued, only now, just for fun, it became a wake-from-sleep issue, instead of a go-to-sleep issue. But with the same Emmy Award-Winning flashing light show on screen.

    G5 #2, I hardly even knew ye. Declared DOA, due to hardware issues of unknown variety, just three hours after unpacking. Back in the box it goes to Apple, and I will await replacement #3. Wish me luck.
    ( I kept a video camera handy and recorded all this bad behavior. Left a copy of the riveting footage on the desktop of the machine for Apple to review, should they want to.)

    (added 3/15/2006)
    "I posted this in the forums but I got 3 random shutdowns today with my Quad G5. I'm on it now typing this and it hasn't shutdown yet but I just wanted to let you know for the web site. I'm gonna keep on using it till it happens again but I'll update my post in the forums by tonight with more info if it happens again or not...
    -Dean P. "

    I asked Dean if he was using an UPS (if so stop using it as a test) and if he'd reset the PMU.

    (added 3/15/2006)
    "I have a Mac G5 2.0Ghz Dual Core that is 3 months old. I was having the shutdown problem which progressively got worse until the machine would no longer boot up. Apple replaced the power supply under warranty.
    -David "

    (added 3/15/2006)
    "I have seen exactly this issue with a DP (not Dual Core) 2.3GHz G5. It is just like the power cable gets yanked out of the back of the tower. My vendor ultimately replaced the tower, with no further problems.
    I know that you are asking about DCs; (they were mentioned in the first reader post on this), my point is that maybe they inherited the issue from the previous generation.
    That makes 3 dual G5s out of 3 that I have dealt with that have some kind of weird, OOB issue. Not a big attaboy for Apple's QC these days. keep up the magnificent work on the site!
    best regards
    -andrew "

    Knock on wood - I've still got my Dual 2GHz G5 (2003 model) and have never had this problem, although I did have my Power supply replaced in early 2004 due to a bad fan bearing. (Was also hoping the replacement (a later rev) wouldn't have the chirping/squealing but it did... I finally got used to it and even stopped using CHUD tool's Disable NAP mode to stop it.

    (added 3/14/2006)
    "We have seen this same problem. The machine would turn off randomly and completely with seemingly little provocation. It was partly exacerbated by ambient temperature-it wouldn't exhibit the behavior in the SoHo Apple store (highly chilled by AC) or in our office (contractors hadn't connected the heat yet), but it would shut down in our server closet (~75-80F) and at the client's office. A replacement of the power supply was in order, and its been running like a champ since.

    The new PSUs are much higher wattage: 700w for the single chip dual core machines, and a full kilowatt for the Quad. They do use non- standard power cords. Anyone who has a few in the office should order a replacement cable to have on hand- Apple service centers should have them available, and I'm sure they can be tracked down elsewhere.
    -Mike "

    (added 3/14/2006)
    "Here's one tale (although Apple are clearly being responsive, despite the intermittent and location sensitive nature of the problem)
    G5 Quad won't stay on at forums.whirlpool.net.au/forum-replies.cfm?t=466271&p=1.
    -pontipak "

    (added 3/14/2006)
    "I dont have a dual core, but I do have a dual 1.8 and the thing has occasionally just shut down...once right in front of me. It was a major shock to see...I thought the computer died. But I switched the power cord and it seemed to fix the problem.
    I later read and learned that the G5's power units are reset by unplugging the cable and reconnecting. I suspect that the same problem is occurring in the dual cores.
    -Benson "

    I'd read the same thing in the past and asked Scott to have his friend try that.

    Another reader brings up an issue that has come up in the past (if you're using an UPS, also make sure it's rated highly enough. When troubleshooting random shutdowns, if you use an UPS try a test without using it - direct system connect to wall AC socket.)

    (added 3/14/2006)
    "Since I have found your site extremely useful in the past, I thought I'd try and contribute my 2 cents about the dual core G5 and intermittent power failures and a possible cause.

    I have a G5 Quad, and previously a mirrored drive doors G4 both which seemed to have this problem. I say seemed, because I have now come to the conclusion (albeit not 100% certain) that the problem lies not in the Mac, but in my UPS or (in someone else's case) possibly a power strip.

    Although on a major overage the UPS will shut down and beep, I have found that this failure also happens when the UPS gives no indication that anything has happened. I have since removed all but the essential electronics (those which are expensive and don't want to risk plugging directly into the wall) and the intermittent failures have all but disappeared. I did have the first one (since removing the non essentials) last night after about 2 months with no problems... However, I suspect there still might be one too many devices plugged into it (or tapping too much power from one outlet).

    I am too lazy (and cautious) to test this, but it should be very easy to do for those experiencing problems and having the motivation to try. I would think most people that own "high end computers" plug them into some type of surge protector, and therefore it could very likely be overloaded or the cause of the problem. My Quad G5 draws a LOT of power, and can heat up my office in about 15 minutes if I close the door!

    It may seem obvious to check the UPS or power strip at the first sign of trouble, but it was something that eluded me for a long while.
    Hope this helps. Thanks for such a great free resource
    -S. "

    A couple other readers mentioned an UPS at fault also:

    (added 3/14/2006)
    "Re: shutdowns
    We had this happen to one of our dual 2GHz G5s (rev a, not dual core) and the problem turned out to be the UPS that it was connected to, which had developed a fault. On the Apple discussions site there were several people who had the same problem.
    - rob.k "

    " I had a problem that sounded like this, but it was not the Mac power supply, but the UPS I was using. It was not large enough for my new Power Mac Dual G5. I purchased a larger UPS and have had no problems. Not sure this helps, but if he is using a UPS it could be the problem.
    -Rob "

    Andy sent a link to a page on a thermal related bug:

    (added 3/14/2006)
    "(from patchwork.ozlabs.org/linuxppc64/patch?id=3765)
    Patch: powerpc: g5 thermal overtemp bug
    The g5 thermal control for liquid cooled machines has a small bug, when the temperatures gets too high, it boosts all fans to the max, but incorrectly sets the liquids pump to the min instead of the max speed, thus causing the overtemp condition not to clear and the machine to shut down after a while. This fixes it to set the pumps to max speed instead. This problem might explain some of the reports of random shutdowns that some g5 users have been reporting in the past.

    Many thanks to Marcus Rothe for spending a lot of time trying various patches & sending log logs before I found out that typo. Note that overtemp handling is still not perfect and the machine might still shutdown, that patch should reduce if not eliminate such occcurences in "normal" conditions with high load. I'll implement a better handling with proper slowing down of the CPUs later. "

    (added 3/14/2006)
    "I'm an academic scientist and manage several OS X workstations for the lab. We have a dual 2.5GHz G5 (not dual core) that appeared to shutdown randomly at about one month intervals after running fine for several months after purchase.

    After a long investigation and calls to AppleCare, it turned out our whole building's power delivery infrastructure is tested the first or second Monday of every month (this is not posted anywhere in the building). This causes a power interruption on the order of a second or two.
    This G5, and only this G5, would shutdown during every test, reporting a "PMU forced shutdown" error in the system log. I have recently put the machine on a UPS, and so far so good.

    I have yet to call AppleCare to see if they would replace the power supply, which seems to have become sensitive to external power as it aged. Interestingly, AppleCare never suggested the power supply, and instead had a disk, the motherboard and CPU's replaced instead (did not work). I found the clues to the power supply on the internet, at great sites like xlr8yourmac, and there were many reports for the dual CPU models as well. Perhaps try a UPS to stabilize the machine? If it doesn't work, then the problem may be internal power distribution vs. external supply?
    Generally, the more information and tests you can show to AppleCare technicians, the better your response will be. Be sure to keep calling and cite the same case number again. Be professional and let them run through their checklists. They often have their hands tied until these checklists are exhausted.
    Hope this helps
    (I mentioned some of the tips above)
    Yes, good advice. I forgot to write that was the first thing AppleCare had me try after running the hardware test (we tried so many things that didn't work, I didn't think to write out the whole list). No luck in my case.
    Thanks for a great resource for Macs. I've been reading it for a long time.
    -Jeff. "

    (added 3/14/2006)
    "I have the random shutdown problem on my dual core 2.3 G5. Apple has been less than forthcoming in even recognizing the problem. I have tried everything I can think of, including disconnecting all external ports to no avail. It just shuts down, maybe once or twice a day at random. Often it takes more than one try to reboot -- it shuts down during boot right after the spinning gear and before the progress bar.

    With an earlier version of iTunes it would shut down consistently every time I launched iTunes -- I began to suspect an internet connection, if that's any help.
    (he later wrote)
    Thanks for your response. Yes I tried resetting the PMU, disconnecting all peripherals (one USB scanner had an effect, but the problem persists without it), and everything else I could think of. I can't find anything in the logs, the power just shuts off like the plug has been pulled.
    (I asked if he was using an UPS and if so to stop using it as a test.)
    Digging around in forums etc. I found a few hits on this problem that implicated the power supply on this model (G5 dual core 2.3 G), but Apple support was no help.
    -Rick K. "

    (added 3/14/2006)
    "I have a 2Ghz Dual Core G5 model - it's a BTO with more ram, larger hard drive and 7800 GT, so obviously it should put more strain on the PSU than stock model (ran it through stress-testing after I got it actually).

    The only problem I had was the powerstrip I was using to plug the tower into the wall could not handle the load from the G5. At first I didn't notice, because the other devices plugged into the powerstrip were operating ok. Upon closer inspection and swapping for a newer more heavy-duty powerstrip it's been fine.

    Oh, I guess there is one thing of very obvious note that should be stated: the power cord that plugs into the Dual Core G5 towers (the one shipped from Apple) features non-standard form factor to fit into the PSU (so you have to get one from Apple), but the problem with them is that they do not fit very securely. I say that in the sense of comparison to those from the vanilla PC world, and I would defiinately suggest do NOT arc that cable to the side mere inches from where it connects to the tower - let it dangle straight-out for one foot and then angle the cord towards your plugin outlet strip.

    FYI this model was shipped out 2005, so may be an older revision than the person's that has the random shutoff problem. IMO Apple should replace the PSU, but first questions: did the owner check the Diagnostics page in the System Profiler? What about the System.log (launch Console, or try dmesg in Terminal), does it spit any errors? Last thing I would ask is if the owner tried re-seating the RAM, and only ONLY if experienced.

    I know these are all obvious troubleshooting tips, but even experienced users forget atleast one of them from time-to-time :)

    BTW is the owner's installed OS X patched or are they shipping 10.4.5 on discs now, because if it is a newer build than the public web version that may be an issue. FYI console.log reports "Mac OS X Version 10.4.5 (Build 8H14)" here.
    Best Regards, Jonas "

    (added 3/14/2006)
    "I'd suggest your reader with the random shutdown problem check the system logs. On one of our clients' G5 machines - not a dual core, but similar problem - the system reported a 'thermal runaway' and then unceremoniously shut down.
    If that's what it is, Apple will fix it. But you've got to go through the system logs to see if that's what's happening.
    -Marc D. "

    (added 3/14/2006)
    "I had the exact same problem on a Dual Core 2.0 purchased in November. It was actually a replacement machine: this first one had major problems and had to be returned. I took the second machine into the local (Sacramento) Apple Dealer and it took them two weeks to replace the power supply. It would have been much faster if I would have fallen for the ransom, also known as ProCare.

    Out of the many Macs I have owned, this one is the only that I could recall having any problems.
    -Bob P. "

    (added 3/14/2006)
    " How about this:
    No random turn offs.
    But, I just noticed that LEDs #3,4 & 5 (Red, yellow and green) are lit now. They were not this way last week.
    According to the LED reference, these shuld be on IF the air deflector is removed (it is not). The first two diagnostic LEDs suggest: Check operation of the air deflector sensor; Replace Power supply. The third suggests sensor; Replace logicboard. This G5 is three weeks old. Took a week to get in all the applications, configure and setup for workplace.

    -Did anyone notice the LEDs prior to the powersupply failures?
    (It's not clear if those with the problems were PS or thermal/control related.)

    I have to find this Air Deflector Sensor board. Even Apple's Service Source mentions HOW to remove it but I can't locate it in their schematic...

    Well, it is under warranty. Though the local ASP is not someone I would like to leave my G5 with for two weeks...
    -Ed "

    On the original G5s at least if the Deflector was removed the system Fans would kick into high gear.

    (added 3/14/2006)
    "It's possible that random shut downs are not a PSU problem, but a cooling problem. I had this with an older dual 2.5 which would shut down randomly and then not be able to boot until I waited 5-10 minutes. It took me a long time to diagnose - I finally thought to download a temperature monitor utility, and saw that one of the processors was running at over 98 degrees C (that's about 200 degrees F!).
    -Jim W. "

    (added 3/14/2006)
    "I have a dual core 2.3 and while it does not randomly "shut down", it has on occasion randomly gone into deep sleep, even though energy saver is set to never sleep. When I wake it from sleep after this occurs, I often get a message from Temperature Monitor stating that the system's sensors had stopped working and that there is possibly a problem with the system or that another application is causing a problem for the sensors.
    This message never appears when I intentionally put the computer to sleep by using the Apple Menu. I bought this Mac in October and this problem did not begin to appear until a few weeks ago. I have not installed any new software in the past couple of months other than updates in the System Update control panel. It is strange, but it has not caused any serious problems yet. I had read that people using 220V were experiencing problems with the power supply, but I am using 110V power with mine.
    -George C. "

    (added 3/14/2006)
    "Was working on my Dual Core 2.0Ghz G5 last week and heard an electrical short coming from the machine then the loud pop. The machine went down followed by burnt electrical smell coming from the machine. Quickly unplugged it.

    I too am reading more and more of PSU failures in the G5s. First Mac I have had a PSU failure in.
    -George "

    (added 3/14/2006)
    "My friend is the one with permanent hearing damage from the PS exploding that's mentioned about half-way down in a report at macintouch.com/readerreports/powermacg5/topic4026.html. There are A LOT of people on there that have been having problems. As a tech responsible for a bunch of Mac's, he now has others turn on new computers instead of doing it himself.
    Regardless, this is a pretty well known (and flat out BIG) problem.

    (added 3/14/2006)
    "We have already reported about PSU problems in PM G5 dual core (Feb 2006) at hardmac. (2006-02-15/#5135, 2006-02-16/#5145)
    Many unlikely owners have reported the weird noise when moving their PM G5, a bit like if screws were moving freely in the PSU. Other did not mention anything, just a blowing PSU killing in most of the case the motherboard and the processor.
    Apparently if it linked to the PSU but not clear if it is directly due the PSU manufacturer or to a unproper assembly of the PSU in the PM G5.
    Regards, Eric
    PS: most of the reports were made from european users. Is it again a defect affecting only 220V-based countries?"

    Reports from those with No Problems: (to be fair here's the replies from those that have not see a problem. I was flooded with mails on this - impossible to post them all but wanted to post a good sample to show that not everyone has seen this problem.)

    (added 10/5/2006)
    "Hey Mike I became a tad worried when I checked the main news page on Xlr8yourmac.com today to read of the problem with a dual 2.3GHz G5 towers (Oct 4, 2006 report above on random shutdown), since I just purchased a refurbished unit from Apple. I did make sure to buy an Applecare warranty extension though, just in case.

    I have had the computer for just short of one month now, and just like all my other computers cracking RC5-72 keys for our Xlr8yourmac.com Distributed.net RC5 challenge, it is on 24x7, which of course is a good way to test the machine for any heat or power related issues. So far (knock on wood) I have not had any problems with random shutdowns, except for when my 2 year old son pressed the power button. I can only guess that since this machine is a refurbished unit, that it may have had the problem, but Apple fixed whatever was causing the problem.
    -Leo "

    (added 3/15/2006)
    "I've been using a Dual Core 2.3 Ghz machine since early January with no issues like this what so ever.

    The last week we've been running it HARD with an extra Fiber + Kona LHe video card in it editing uncompressed HD.

    Everything stock except extra WiFi/Bluetooth and RAM (and now the last week, Fiber and Kona card).

    I'm currently installing a Quad G5 at work - can repport later if I have issues there.
    Erik L.
    Production Tech (Sweden) "

    (added 3/15/2006)
    "I have a dual core G5 2.3ghz w/ 4mb memory and haven't had spontaneous shutdowns per se. I've had a number of unexplained crashes where all has stopped. Otherwise, system works ok.
    -Clifford "

    (added 3/14/2006)
    "As you mayy recall from my latest Drive Compatibility Database entry, Apple replaced my defective G5 1.8GHz DP Rev A PowerMac with a new 2.3GHz Dual Core PowerMac, and it's been perfect from the get-go. No issues at all, and I'm running PCI Express FireWire (SIIG) and USB 2.0 (Koutech) cards, two 250GB Maxtor internal HDs, BlueTooth/Aextreme module, and 8GB Omni Technologies RAM.

    It's on 24/7, either doing my studio work or running Folding@ Home, so you'd think that in 3 weeks I'd have seen this issue if mine had it. As I understand the new PSU for the Dual Core models, it's a 710-Watt unit for my model, and the Quad has a 1000-Watt PSU.

    Sorry to hear about the other nice Mac owners having their problems, but nothing to report here.
    Best Regards, David C. "

    (added 3/14/2006)
    "I have been using my G5 Quad for a over a month without so much as a hiccup. 2GB RAM, Quadro FX, 500Gig single HD, bluetooth + airport, latest 10.4.5.
    I'm certainly not pampering it; running Maya 7 and ZBrush 2. I too have never heard of any G5 power supply issues. Compared to my G5 dual 2.7, the Quad runs a bit cooler even. Hope this helps.
    -Dave "

    (added 3/14/2006)
    "I have a 2.0 Dual core G5 that has been in operation for about a month with no problems as described.
    -Jim "

    (added 3/14/2006)
    "Received my PowerMac dual core 2.3 GHz last November and it's been rock stable and very quick. No problems whatsoever, and I'm on it 8-10 hours every day, seven days a week. I ordered it with 2 500 GB drives and 1 GB RAM, then added an additional 4 GB Samsung RAM.

    It has always been plugged into an uninterruptible power supply, which is a good thing, as it would otherwise have been taken down several times with power outages, not to mention voltage fluctuations. I've wondered whether some of the complaints about power supplies on similar PowerMacs may be tied to AC power problems such as voltage surges, "brownouts" and the like.

    This is head and shoulders the best Mac I've had, and I've had 14 to date. I run large databases that are CPU/memory intensive and performance is outstanding. It's also a quiet machine. I can hear low background noise of air movement (barely noticeable), but fan speeds never rise to a higher level in use. The optical drive is noisier, but not excessively so.

    Bottom line: I'm extremely pleased with the PM dual core 2.3 GHz and expect to get years of service from it. As I'll be testing software for Intel Macs, I plan to get a MacBook Pro down the line. Although performance on the MacBook Pro looks good, I expect the additional RAM in my PM will keep it well ahead of the MacBook Pro performance for my purposes.
    Down the line, I expect Apple to release faster machines than my PM DC 2.3, but as I'm already getting most searches completed in a few milliseconds, I expect to be satisfied with my PM for a few years. :-)
    Regards, Bill D "

    (added 3/14/2006)
    "Never had this problem with my Quad G5 since late November when I got it. And it's under heavy use.
    -McD "

    (added 3/14/2006)
    "i have a quad G5 (dual-dual core) and it never randomly shuts down. its been running 24/7 since i purchased it (december '05).
    -D "

    (added 3/14/2006)
    "I too have a Dual Core 2.3Ghz G5 (purchased in Nov '05), and haven't had any problems with it at all.
    I've added a second 250GB hard drive (for a total of 500GB) and 1 GB of after market RAM (for a total of 1.5GB). I've got two monitors (one a 20" cinema display and a 17" Samsung) - and the standard Nvidia 6600 video card. In terms of peripherals, I've got my iPod dock, a HP3970 scanner and a Deskjet 935c printer.
    The main job of the computer is compiling code (although there's some UT 2004, Doom 3 and Soldier of Fortune II), and the iLife 'thing'. It's on during the evening, and almost all weekend for all weekends.
    This has been a very solid computer for the time I've had it.
    If you need any more info, please feel free to email me.
    Best Regards,
    -John C "

    (added 3/14/2006)
    "I have a dual-core G5 (2.3 GHz) and have *not* seen the reported power supply shutdown problem. I tend to leave my machine on all the time as it is currently also serving as a backup server.
    -Russell F. "

    (added 3/14/2006)
    "Dual Core G5 w/ (1) stock 250GB plus (1) 400GB plus 4.5GB RAM
    No spontaneous shut down problems. Computer is left on always.
    Mark B.
    Systems Integration Manager "

    (added 3/14/2006)
    "The only issue I have seen from my DC 2.3Ghz G5 is the HD failed (after about 5 months). I had some odd issues before that, but at this time I can only attribute that to a HD that was having some issues before it failed.
    Also, I think some of the instability was caused by CCC 2.3 (It was worked fine for Mac OS X 103x/Panther, but this system - as you probably know runs Tiger and comes with 1042 install discs).
    I have a new HD and did a erase & install and the system has not had a crash since (its been about 3 weeks of 24/7 running).
    HTH, -drx "

    (added 3/14/2006)
    "I have a Dual Core G5 2.3 with 2Gb Ram, stock HD, 7800GT nVidia video card, airport/bluetooth and have not had any problems, let alone the random shut down problems.
    -Jim S. "

    (added 3/14/2006)
    "I have an Oct 05 Dual Core 2.3 Ghz PPC with 4.5 GB Ram connected to a 23 inch Apple Display and have had no problems with anything. Fast, quiet, no troubles.
    -Roland L. "

    (added 3/14/2006)
    "I have been monitoring reports of this, as well as power supply failures in DC G5s, on Macintouch.
    I have a 2.0 DC G5 that has been in service for approximately four months without any such issues (knock wood!). It remains "on" about 16 hours per day, and is dropped into sleep the rest of the time...
    - Edward R. "

    = Popular Links =

    macOS Updates
    and also

    Mini-ITX Hackintosh

    Dual M.2 NVMe
    SSD PCIe Card
    (Mac Pro 5,1)

    Apple Guides

    Display Tips

    LG OLED TV Firmware

    LG OLED TV Tips

    Audio/Home Theater Updates

    TV, AVR, and Disc Player Tips

    = back to www.XLR8YOURMAC.com =

    = Other Site Topic Areas =
    Mac Upgrades/Repairs | Storage | Video | Audio/Home Theater | OS Updates/Tips/Wi-Fi

    Copyright © 2006-2010. All Rights Reserved.
    All brand or product names mentioned here are properties of their respective companies.

    Legal: Site Privacy and terms/conditions of use.