ALSA: bad sound with low CPU load

[Aaron Burt <aaron@speakeasy.org>]

Basically, sound comes out as a hissing, garbled mess *unless* I load
down the CPU.  A kernel compile seems to do nicely for this purpose.

I've been seeing this behavior in the late 2.6.0-pre kernels through
2.6.1 plain and -mm1.  It happens with preempt and HPET both enabled
and disabled.  I haven't yet found what exact kernel version the
problem starts with, and I get no sound with the OSS drivers, so I
can't test them ATM.  I plan to narrow things down if possible, but
that takes time.

System is an Athlon at 1145 MHz on an ECS K7S5A (SiS 735 chipset)
running Debian Sid with ALSA-base v0.9.8-3.  The problem happens both
with the onboard i810-compatible sound and a CM8738 PCI sound board.
(Note that both are fixed at 48000 Hz.)  I'm tempted to buy 'n' try a
SoundBlaster-PCI card from FreeGeek.

I'd be happy to provide further info, but didn't want to start out
with a super-long message for something that may be obvious, if not
visible in Google or LKML.  Please reply to the list; I'm subscribed.

Thanks in advance,
  Aaron