" (G4 Digital Audio 733 w/Newer Tech 2GHz 7448 CPU Upgrade, running 10.4.9)
I recently ordered the OWC PCI sata card they sell for like $50. I also got two Western Digital ("Raptor") 150gig 10,000rpm with 16meg cache. I removed the old SCSI 10k and apple OEM card, as well as firmtek ata-133 card and seagate ata hard drive as well. So in summary, computer only has two hard drives in it now, the two sata raptors. cloned the old two drives onto the new ones so system is up and running all good. However I am now noticing an unusual behavior.

(Log Errors)
May 18 02:32:35 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - Error: attempting to clip to a
position more than one buffer ahead of last clip position (a8,122a)-> (ab,2293).
May 18 02:32:35 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - adjusting clipped position to (ab,122a)
May 18 02:32:36 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - Error: attempting to clip to a
position more than one buffer ahead of last clip position (ac,2a93)-> (b0,181a).
May 18 02:32:36 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - adjusting clipped position to (af,2a93)
May 18 02:32:57 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - Error: attempting to clip to a
position more than one buffer ahead of last clip position (e9,381a)-> (eb,c83).
May 18 02:32:57 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - adjusting clipped position to (ea,381a)
May 18 02:36:02 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - Error: attempting to clip to a
position more than one buffer ahead of last clip position (2dd,a23)-> (2df,2eef).
May 18 02:36:02 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - adjusting clipped position to (2df,a23)
May 18 02:37:48 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - Error: attempting to clip to a
position more than one buffer ahead of last clip position (3fd,628)-> (3ff,5dc).
May 18 02:37:48 Omega-1 kernel[0]: IOAudioStream
[0x2aeaf00]::clipIfNecessary() - adjusting clipped position to (3fe,628)

This happens ANY time there is a marginal amount of disk access, doesn't have to be a lot, just simple things like launching a program or whatever. whenever that error comes up all mac audio actually stops for like 1-2 seconds. As if the mac can't produce audio and access the two hard disks at same time. I'm not sure if anyone else has this problem or what. I'd definitely want to find out though. Included is a report of my frankenmac's configuration.

Upgrades are as follows: (only listing main hardware, no external devices like isight etc, That's all in report anyways though.)

G4 Digital Audio 733
CPU: Newertech 7448 2GHz G4
Ram: 3 Apple 512MB PC133 Dimms for total of 1.5Gig Ram
Video: Geforce 4 Titanium w/128MB video memory. using DVI to go to 20 inch Apple Cinema Display LCD.
PCI Cards: USB 2.0 card (forget which brand, whatever walmart carries, heh)
OWC SATA Card using two internal channels.
2x SATA Western Digital Raptors (10krpm and 16MB Cache w/150Gig space each.)
Both formated HFS+ Journaled, Setup so one is boot drive and applications drive and other is a dedicated documents only drive.
CD Drive: Upgraded to a Pioneer DVR-108 OEM with latest 1.20 firmware installed.
-Adam W."

If anyone else has seen a similar problem (or not), let me know. Are there any 3rd party Audio apps/addons installed?
Can you try a 'clean' OS X install to try to see if it shows the same problems? (maybe with a pre-10.4.9 version - and see if spotlight is still indexing the drive, as that takes a performance hit, a significant one on older macs here)
(Update - see below - Adam later wrote that using a Seritek 2port card solved the problem.)

(he later wrote)
"Spotlight did index drives and the audio clipping happened excessively during that. However I paid it no mind since I knew spotlight was cpu hogging. However the problem persists during any disk access still and spotlight is idle. I haven't benched data rates yet but I did note that when I cloned the scsi-160 drive that was a 36gig 10k seagate cheetah to the first WD raptor 10k drive the cloning data rate shown in superduper was only 5-7Mbps. However I don't know if that's from a slow data rate issue or just cause superduper had to evaluate files at same time. Ill try to bench it later.

I have no other sata drives to test but I did order some different sata cables to see if that's problem. I would also be curious to know cable types and brands others having problems have used.

As for clean installing os x. That's a pain in the butt. But I will use the second drive and temporarily make it an os x boot drive as a clean install test. If that works then I'll redo main drive.
-Adam W. "

Another Digital Audio (G4/533) owner with the same controller card but different HD wrote he's seen the same thing:

" Mike, In response to Adam W. who was experiencing the IOAudioStream::clipIfNecessary() error after installing the OWC SATA card and a WD disk: I am having the same problems with a Hitachi 160Gb SATA drive connected to the OWC card.
Other than the SATA card, my system has little in common with Adam's:
Digital Audio Dual G4/533
1GB RAM (256, 256, 512)
One Hitachi SATA 160GB HD attached to OWC SATA card
No other PCI cards installed.
Radeon 9600 Pro w/Dell 1905FP monitor (DVI)
Pioneer DVR-127D CD-R/DVD-R drive

I had installed the card initially under 10.3.9, prior to upgrading to 10.4, and it showed the same symptoms.

Other than the audio issues, performance of the card seems to be good. I did have some problems with occasional wake-from-sleep corruption of the boot partition, so I simply stopped putting this machine to sleep and just shutdown when I'm going to be gone for awhile.
My conclusion was that it was the card.
-Rich"

(Update - see below for a later mail from Rich on the problem being solved now.) for This reminds me of the audio dropout issue seen years ago with PCI IDE cards in older Macs - where just playing an audio file or QT Movie from a card connected drive (no other disk I/O) would have audio dropouts. The fix that was later released by the card vendors for that typically reduced drive performance. During the review of 5 PL CPU Upgrades back in fall 2005 here, I used a 2-port Seritek PCI SATA card in a 2001 Quicksilver tower with an SATA boot drive and didn't see any audio dropouts in weeks of testing. (BTW - Adam later sent a link to this page that comments on this issue with some SATA PCI cards.)

Update - On May 24th Adam wrote he swapped in a Sonnet (re-branded Seritek) 2-port SATA card, which doesn't have the problem.

" Just installed the sonnet 2 port SATA card (the rebranded Seri-Tek1S2 card). Using itunes right now while copying a 7 gig file from one drive to other and writing this email with zero audio clipping. So clearly it's not a problem with OS, or WD drives (it was not drive related, a 2nd report previously above noted he saw same thing and was using an Hitachi SATA boot drive), it is the OWC card. Whether it's a bug that can be fixed with a firmware update or a problem with hardware itself, it was clearly fixed by changing to a different card.

SeriTek/1S2 v. 5.1.3,11/22/05, 23:47:18:
Name: Seri-Tek1S2
Type: ata
Bus: PCI
Slot: SLOT-5
Vendor ID: 0x1095
Device ID: 0x3112
Subsystem Vendor ID: 0x1095
Subsystem ID: 0x3112
ROM Revision: 5.1.3.1S2
Revision ID: 0x0002

(he later wrote)
I did notice that the peak of the Seritek was 53MB a second for a drive to drive copy and with the OWC card it was 57MB/sec, it's possible the firmware on controller is just a little smarter about limiting the bandwidth not to starve the bus... just a theory. (the 'fix' years ago for audio dropouts with PCI IDE cards in older macs also resulted in lower performance)

I noticed one annoying thing about seritek though. The hard drives do not show up in system profiler anywhere. With the OWC card for some reason they listed under ATA instead of sata, with Seritek card they don't list under ata or sata. they list nowhere.
-Adam W. "

I (and others) saw that same thing in the past with that card. There was some notes on that last year (or more) ago and I think I wrote Seritek about that back then and IIRC it was to be 'fixed' in a later OS X update, but apparently not.

(June 11, 2007 update) - Rich sent a follow-up saying the problem seems solved now, after applying some recent apple OS X updates:

" Hey Mike!
You might want to check with the other Xlr8yourmac reader who was having audio dropouts with the OWC SATA card. (Adam mentioned he had already bought/installed a different card though.-Mike)

Somewhere along the line with the most recent updates, the problem seems to have gone away (at least for me). I can run iTunes and even when intentionally thrashing on the boot disk or the one containing the music files, it won't skip. Looking in the logs, there's no more of the IOAudioStream::clipIfNecessary() notices either. I haven't changed any of the setting on the Mac in anyway.
I'll keep an eye on it, but maybe something got fixed somewhere!

(Any idea which of the updates you think may have helped?)
Unfortunately, I don't. I was a few behind and just let Software Update do it's thing. If I had to guess, it might have been the Quicktime 7.1.6 update. I wasn't expecting any joy or I would have payed more attention. :-)
-Rich "