STP uses 100% of processor

Question

On my PowerBook G4 (1.67GHz), Soundtrack Pro 1.0.2 uses all available processor time when recording. The audio in the recording also skips, making it unusable. Activity Monitor shows 100% processor usage and shows ST's as about 80%ish and the random system processes totaling at about 20%ish. ST's usage goes down immediately after stopping the recording.
This happens even after a fresh restart and logging in to a dedicated account that's only used for production work (so there's no other apps running or random background processes or widgets).
I've filed it as a bug report to the Soundtrack feedback page, but I was wondering if anyone else has experienced this problem (most websites I go to say that ST is pretty easy on the processor) and if so, how it might be fixed.
TIA,
Chris

Answer 1

I'm using a Mackie Onyx 1220 with a Firewire card, using the built-in Core Audio drivers. The problem also occurs when I use the basic on-board mic or line input (just for testing...I would NEVER run anything critical through those!)
I have 1GB of RAM. The problem occurs with both the internal hard drive and an external 400GB Firewire 800 drive. It also happens in both my normal user account and also a "production" account in which I have tried to leave all the settings as stock as possible (and not installed any system modifications or other processor-using apps).
The skips occur every few seconds. There's nothing else trying to use the CPU--when ST isn't recording, usage drops to ~10-20%. I haven't specifically looked for disk activity, but I have been having problems with iTunes and other media apps skipping based on disk write usage (see http://discussions.apple.com/message.jspa?messageID=787719 for an in-depth--and still unsolved--look at this problem). Perhaps this is related to the skips in recording. However, the CPU-usage problem, I don't think, is related. Logic records with no difficulty and ~20-40% CPU usage.
I haven't yet tried the drastic step of reinstalling Tiger from scratch, as I have many settings (both UI and unix) I'd like to preserve, and I seem to always be too short of time to undertake a large project like that. But if that's the only way to solve it.
Is there a way to inspect the STP process to see what loop is using all of the processor time? Same for the disk usage part of it (to try to identify what's causing the skips--core audio buffer underruns, etc.)?
Thanks for your help.
Chris