Dan Eischen, deischen@iworks.InterWorks.org, the author of the
aic7xxx driver, also recommends not to use stock 2.0.30 aic7xxx
driver. He instead pointed me to his "July27" driver,
available from ftp://ftp.pcnet.com/users/eischen/Linux/July27/
(mail me if you want it in unified diff format)
I installed this driver release, and the problems are gone ever since,
the machine is running stable again. It also cured random hard locks
on a friend's machine (dg2fef@afthd.th-darmstadt.de) when serving
with Samba. On two other machines (btw. all having an Adaptec
2940) it also performed very well.
I couldn't test exotic SCSI hardware, I only used it with
SCSI disks (removable and fixed), CDROM drives and a CD Writer.
I'd like the July27 driver to be part of 2.0.31...
Tom