Re: 10.2 USB recording problems?
Re: 10.2 USB recording problems?
- Subject: Re: 10.2 USB recording problems?
- From: Mark Cookson <email@hidden>
- Date: Thu, 12 Sep 2002 11:01:54 -0700
On Thursday, September 12, 2002, at 08:37 AM, Kurt Revis wrote:
On Thursday, September 12, 2002, at 08:21 AM, Mark Cookson wrote:
USB is not perfect, but in general, on Mac OS X 10.2 (Jaguar), under
reasonable load, USB recording and playback is glitch free. We have
seen CPU loads of about 85% before glitching happens. At 85%, the UI
is very unresponsive (menus take 20 seconds to draw, mouse jumps
around, etc.).
What exactly do you mean by "CPU loads of about 85%"? I can easily
get to 100% CPU utilization (just by compiling an application) and the
machine stays responsive, just as it should. Do you mean a load when
85% of the CPU is taken by the kernel, or by CoreAudio, or...?
When the load is taken by the real-time thread, meaning that lots of
other threads are loosing out on their appointed time to run because
they aren't high enough priority.
If you have the CPU busy doing low priority things, CoreAudio and the
USB system aren't stressed because the kernel tasks and secondary
interrupts have priority over the compiler. When it's an audio thread
using all that time, things get sticky because almost nothing can
preempt the IOProc's real-time thread (including the USB secondary
interrupts).
--
Mark Cookson
Engineering Droid
Apple Computer, Inc.
Core Audio CPU Software
6 Infinite Loop MS 306-2CW
Cupertino, CA 95014
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