Pb with simultaneous SATA and ALSA I/O

[Dominique Dumont <domi.dumont@free.fr>]

Hello

I have some problem using the SPDIF output of my SB Live card while
performing I/O on my SATA drive. (See [1] for the whole story on the
ALSA mailing list)

My Yamaha amplifier does not recognize the AC3 (Dolby digital) stream
from the sdpif plug while performing I/O on my SATA drive.

If I have a lot of I/O (e.g. running md5sum on a 4Gb file), the AC3
stream is completely broken.

If I have some I/O (e.g. reading a Hi-def movie), I get some AC3
drop-out even if the CPU is about 50%.

I have the same result with DTS output.

With PCM output, I've noticed a hi-frequency distortion, which means
that the interaction between SATA and snd module occurs several
thousands time per second.

My set up is:
- Debian Linux kernel 2.6.17
- Sound blaster SB Live 5.1 (snd_emu10k1 module)
- SATA drive (sata_sil and libata module)
- A7n8x deluxe mobo
- AMD XP 3200 

So far I verified that:
- AC3 output works fine when SATA drive is left alone
- AC3 output works fine when running md5sum on a PATA drive
- DTS output works fine on the mobo SPDIF output (snd_intel8x0 module)
  even when running md5sum on the SATA drive. (cannot try AC3 stream
  because of Soundstorm chip :-( )
- Preemp kernel option does not fix the problem
- when running md5sum on SATA drive, alsa driver report a starvation
  (xrun) every few seconds, not thousands of time per second.

Could someone shed some light on this problem ?

What can I do to help debug this problem ?

Thanks


[1] http://www.mail-archive.com/alsa-user@lists.sourceforge.net/msg17399.html