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Review: PowerForce G4 350MHz G4 CPU Upgrade for PCI Macs By Mike Published: 1/16/2000

Intro | Benchmarks | Appl. Tests | Software Controls | Installation | Specs/Design | Summary

Disclaimer: This page is for reference only. Removing the CPU or performing other upgrades/modifications to your Mac may void your Apple warranty, cause damage to your computer or result in personal injury if done improperly. Consult the upgrade's owners manual for complete instructions or get qualified help if necessary. (Tens of thousands of Mac owners upgrade their CPUs every year, but consult the product manual for complete instructions and precautions.)

This page provides a brief summary of the installation of the Powerforce G4 CPU upgrade in CPU card slot Mac. The Powerlogix printed manual provides more detailed instructions for buyers of the upgrade, including illustrated guides for 73/75/7600, 85/9500, 86/9600, and a Umax/Power Computing (picture is of a PowerCenter Pro MT) models to clarify installation in specific models. This page simply gives a general overview of the steps involved, potential pitfalls and suggestions to ensure a smoother installation. What's Included The PowerForce G4/350 CPU Upgrade package includes: 350MHz G4 CPU card with 1MB of Backside Cache Illustrated, printed Installation Guide/User Manual. 'Emergency Boot' floppy (see Software Controls page for info) CD with Control Software, Utilities and LinuxPPC Disposable Anti-Static Wrist Strap (use it) Rather than a registration card, the manual requests you register online at www.powerlogix.com/support/register.htm. Switch Settings: The PowerForce G4/350 card ships with the switches set for a 50MHz bus speed, 7x Bus/CPU ratio (50Mhz bus times 7x ratio = 350MHz CPU speed). I highly recommend you leave the card at the default speeds. (Even tweakers should run the card for a week or so at the stock settings before experimenting with other speeds, just to ensure the upgrade is reliable in their system.) I also strongly recommend you remove any L2 cache dimm (if possible) before installing the card as too-slow L2 cache dimms are a major cause of CPU upgrade problems. If your Mac model is a Power Computing PowerBase, set switch #8 (the last switch) to the ON (down) position. This switch should only be set ON for Powerbase models. If you're unclear on the switch settings, Powerlogix has posted a downloadable switch demo. Installing the Software: Before installing any G4 CPU upgrade in an older Mac (pre-Apple G3 series) make sure you install the supplied software. (Newer Technology models are an exception, as they contain a hardware fix for the Speculative Processing/Speculative Access issues of G3/G4 upgrades in older Macs that is addressed via software/virtual firmware on other upgrade brands.) See the Software Controls page for more information on the Powerlogix G3/G4 Cache Profiler application. Also check the G3/G4 cache profiler version on the supplied floppy disk. Early models contained version 1.0, the current version at www.powerlogix.com as of this review date is version 1.3. Download the current version if necessary. Installing the CPU Card: The following is a summary of the CPU card installation routine: Install the Powerlogix software first, while still running the original CPU card . I recommend booting your Mac with the Powerlogix floppy installed *before* replacing the original CPU card. This ensures the fix for Speculative Access is written to the Mac's Novram before attempting to boot with the G4 CPU card installed. Shut Down the Mac (disconnect the AC power cord to prevent accidental powerups should you inadvertently press the keyboard power-on key, etc.) Remove the case cover Attach the wrist strap and connect it to the metal surface of the Macintosh chassis (Power Supply external case for example). Remove the existing CPU card from its slot If possible - remove the L2 cache dimm. Most G3/G4 upgrade problems are due to too slow an L2 cache. With the G3/G4 card's fast backside cache you don't need it, and especially with Apple's stock cache dimms - most will be a source of problems. Double check that the CPU card's speed settings are correct (the manual has table of settings - don't get the pictures of the switch settings reversed - a long white bar means the white switch lever is DOWN). I strongly recommend you leave the card set to the factory settings for at least several days of heavy use before you think of changing speeds. Insert the CPU card, making sure it's fully seated in the motherboard connector. Press the CUDA (CPU reset) button on the motherboard (hold down for 30 seconds) (You'll have to reset your date and time and some other control panel settings after the initial boot. With OS versions prior to 8.5, make sure you reset the Memory control panel's disk cache setting as well as earlier OS versions default to a very low setting like 96K, which reduces hard drive performance. (Note: Zapping the PRAM or resetting the CUDA switch in systems with a Thunder3D or IXMicro IX3D card can result in no video at boot. If this happens, remove the video card, power up the mac, shut down and then reinstall the video card. Connect the PowerForce G4's CPU fan power connector to a spare power supply connector. If there are no spare connectors, use one from a hard drive or CDROM drive, as the fan has a pass-through connector that allows reconnection to a drive should you need to do so. (An addendum to the manual has an illustrated guide for connecting fan power.) Replace the Case Cover Power up the Mac. Verify that the G3/G4 cache profiler (Control Panels under Apple Menu has an alias to it) shows the correct CPU, Cache and bus speed settings. Verify that Speculative Processing is disabled under the 'Other' tab and that the backside cache is set to be enabled on restart (checkbox). If your Mac has soldered-in motherboard L2 cache (i.e. 9500, S900, etc.) you might want to check off the option to disable it. (See the Software Controls page for illustrations of the Powerlogix control for these settings.) Total installation time was under 5 minutes, but if you want to experiment with other than the default speed you will need to adjust settings and then verify that the new speeds are reliable (I'd suggest at least 12 hours of heavy apps use to verify reliability along with an overnight RAM test or Game continuos demo). Should your system not boot follow the steps in the troubleshooting section of the manual and the tips noted below. If you'd like to see a sample of a Powerlogix manual, visit http://www.powerlogix.com/support/manuals.html. (The G4 model was too new to have the manual listed there, but there are other model manuals that will give you some idea of what Powerlogix's manual contents.) Speed Settings: As noted on the hardware details page, the Powerforce has 8 possible bus speed settings in the range of 40 to 60MHz, and up to a 10X Bus to CPU ratio (10X ratio setting requires a 10X G3 CPU of course). The card ships ready to install with a default bus speed of 50MHz, a Bus/CPU ratio of 7x for a default CPU speed of 350MHz. There's no need to touch the switch settings if you only want to run the card at the default speeds. Adjustable speed cards give you the option of experimenting with other speeds, but first make sure the card works well at the default settings. If you're unclear on the switch settings, Powerlogix has posted a downloadable switch demo. Some manufacturers of CPU upgrades say that a single, fixed bus speed is the best solution. Powerlogix comments on the issue of adjustable bus speeds at http://www.powerlogix.com/support/bus.html. Troubleshooting: Along with the benefits of a wide range of adjustments comes some responsibility. This card allows setting bus and CPU speeds to rates beyond the rating of the CPU and possibly your system's capability. You need to consider the installed upgrade's CPU/cache rating and the limits of your particular Mac (don't start out with high settings that have not been proven reliable in your system/CPU module combination). Although the Powerlogix manual also covers troubleshooting problems, here is a basic guide I follow when experimenting with speed settings in my Macs: Before any major upgrade, especially when experimenting, back up your data just in case. If problems are seen at the default settings, I set the card to a low bus speed (45MHz or less if I don't know the machine history). Never start high and work down - always start low and work up. Otherwise crashes, system lockups, etc. will make troubleshooting a frustrating and difficult procedure. I verify the card is fully seated in the motherboard CPU connector. I double check that the ratio setting is correct (set to so that bus speed times ratio does not exceed the CPU speed). Don't rush, take the time to verify that the settings are correct per the manual. It is important to not overclock the CPU or cache during the process of finding a reliable bus speed - you want to isolate one factor for reliability, not confuse the issue by running the CPU or cache beyond its rated speed. With this particular upgrade's design, make sure the heatsink is not loose (DON'T overtighten the heatsink however - if screwed on too tight you can breat the plastic retainer. Just make sure it's snug. Since this CPU upgrade has a Fan, make sure the fan't power cable is connected to a power supply connector. If the fan is not running, the CPU could overheat. If the system does not boot at the current bus speed setting and I've made sure the card is fully seated and I've removed the L2 Cache dimm (if possible - some systems have soldered-in cache, so de-interleaving RAM or lowering the bus speed are other options). With no L2 cache dimm installed and if all the RAM dimms are of known good quality, try lowering the bus speed . Otherwise, try removing any old or mixed speed RAM (start with 70ns RAM or dimms like the original 8MB ones often shipped with early Macs. Deinterleaving RAM (making sure that A1/B1, A2/B2 etc. slots do not have like dimms installed - put all dimms in the A or B slots to prevent interleaving (see my article on Interleaved RAM). Once the system boots, I verify reliability by running applications that stress the CPU for hours to make sure the card is reliable. Simply booting and running MacBench is not proof. If you own Unreal or Quake, letting the auto-play demos run for hours is a great way to test for problems. As a test for hard drive data errors - try mounting an Apple .SMI file image which will do a checksum test. (Apple often supplies software updates in this format - a good test file is Apple's OS 8.5.1 update which is very large and therefore a better test of data integrity.) Powerlogix also has troubleshooting tips at their PowerForce FAQ. Warning/Disclaimer: Overclocking may not be reliable at all speeds or with all card samples. Although Powerlogix currently honors the warranty regardless of speeds settings, I do not recommend overclocking to others and you assume all risk from doing so. Many owner reports in my 3000+ entry Rate Your G3 Upgrade database indicate overclocking is very common with few failures, but I suspect some reported speeds may not prove reliable after extended use. Also remember failures or problems seen later may not be reported for many reasons (inability to get on the net, or embarrassment to update a rave report with a note there were problems seen later). At the date of this review, the Powerlogix FAQ states they honor the 3 year warranty regardless of speed settings. If you do decide to risk overclocking, remember to exercise caution, as the limited warranty does not cover your data, your time or anything but the CPU card itself. No company can guarantee overclocked speeds or what bus speed will be possible in your system. Buy a CPU upgrade by its rated speed, not an assumption that you can overclock it reliably or will be able to repeat another owner's speeds (even with a similar mac model and upgrade card). Each card/system combination is somewhat unique and reliable speeds can vary depending on CPU lot/batch, installed RAM, cache and other factors.

Summary: The PowerLogix manual contained good information on the installation of hardware and software, troubleshooting tips and an illustrated switch settings page. My rev A manual had a loose leaf addendum sheet with a photo illustrated guide to connecting the fan power. The cooling fan is unique to their G4 models. The only omission I saw was that there was no contact information for technical support (no phone or email tech support information listed). Powerlogix'sContact web page has this information. Perhaps this will be added to the next printing of the manual. Installation went smoothly and the card booted fine at the factory (as shipped) settings. As with any adjustable CPU card - things can be complicated if you want to experiment and push too far on speed settings, since only trial and error can determine what advanced settings are reliable in any particular Mac.

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