Said hangs always occur on heavy disk I/O, it seems... No matter whether I have
NFS mounts (all readonly) or network traffic (ssh) going on, hangs will happen
nevertheless.

Machine is BigSur, 1 B2 CPU, don't know how to identify BIOS versions or
firmware revisions so I cannot give these informations right now. CPU runs at
666 MHz. 1 GB RAM, qla1280 SCSI adapter with 64bit addressing enabled, with two
disks (the one that came with the machine, ie a Quantum, which hosts /home, and
a 40GB Seagate which hosts the rest). Attached is the .config for current
kernel.

The "sleep 1 sec/sync" script, which I run continuously, only reports the
problem to later... When this happens, nothing at all will work, no response
from keyboard so even SysRq is unavailable... Also, the timer bug patchlet
reports the problem to later as well... Much later, in fact.

Before I go on and try to track down the bug, I'd like to know whether BIOS rev
and firmware revisions can be in cause... If not I'll go with kdb...

-- 
Francis Galiegue, fg@mandrakesoft.com - Normand et fier de l'être
"Programming is a race between programmers, who try and make more and more
idiot-proof software, and universe, which produces more and more remarkable
idiots. Until now, universe leads the race"  -- R. Cook