SCSI unstable on a MAC "Quadra 840AV"

[Lukas Walter <lwalter@ee.ethz.ch>]

I have installed Debian GNU/Linux on a Macintosh
Qadra 840AV. The instalation works but from time
to time the machine stops and the only thing i can
do is to press the reset button. It happens when I
try to mount my extern Apple SCSI CDROM. Also when
I install packages (means the HD has a lot to do)
the same thing can happen.

Is ist a problem with the SCSI driver?
(I tried 3 harddisks)

Lukas