> Hi guys,
> 
> First I want to thank all the people who wrote to me on the
> subject. I think I found the problem.
> 
> It became clear that it was a timing problem. Furthermore, I was
> puzzled by the fact that if I had the machine off for a few
> hours, that means everything cold it would work. As soon as the
> thing got warmed up, the failure appeared. That seems to
> indicate that could be related to the fact that the drivers can
> deliver more "juice" when they are cold. My SCSI configuration
> was: two CD-rom drives (a Chinon and an HP), the TK50 and the
> disk (a Seagate Barracuda). So I unplugged the Chinon thinking
> that if I reduce the loading it may work... and Magic! It did!
> The Chinon was perfectly functional, but it seems that it was
> loading the bus too much. So I replaced that Chinon by another
> HP drive, which doesn't seem to load the bus. So everything
> works fine now.  We could say "not all SCSI devices are created
> equal"...

That is a bit like my problems.  I have a box full of scsi cables
(a dozen or so) that I routinely reach into for hooking up A-B or
B-C or whatever.  Alas, a pair of them turned out to be funny.
Get this.....they worked fine with Ultrix, yet died on NetBSD, on
both pmaxen and VAXen.  I am beginning to think that something
like cable capacitance or RF resonances are beginning to affect
the transfer of data.  Are we pushing the data limits for the
old hardware?  Anyone know?  What are the expected data rates
on Ultrix 4.2A vs NetBSD?  I would be curious to know the exact
type of cables you were using, the manufacturer spec, the length,
terminator type, etc?  Theoretically 6 meters should be usable, but
I get about 3 meters on old Suns before the signal dies.  My funny
cables were new, but were no-name brand from the local cable mongers.
I tried several other no-namers and they worked fine, as did an
Apple cable, an IBM cable, and a couple DEC cables.  Any insights
or suggestions are appreciated..... SCSI gets funky sometimes...(:+{{...

.....

> >I also get asc_intr errors on HD accesses occasionally, but they seem to
> >be more spurious interrupt things.

I am still getting a few of these, even after changing cables, so I still
suspect some timing things need tweaking a bit.   I will write down the
exact asc_intr messages tonight.

Bob