> It appears that the work-around for the ESP100 chip variant dealing
> with a select/reselect race was no longer effective.
>
> This was fixed in dev/ic/ncr53c9x, rev. 1.104.
>
> It may or may not solve your problem, but it's worth a try.

Sorry for taking so long to reply, but I was waiting for a new memory
module. :-/

The patch indeed fixes my problem and the quantum drive appears to work
with tagged command queuing.  At least booting does not show any problems
after the patch, and it triggered them each time before.

Thanks a lot for the quick solution!

Michael