> Might be able to get some clues with a logic analyzer, which
> I happen to have.  Not sure how easy that would be.  I thought
> the Crimson was VME?  VME bus is pretty well documented, so it
> might be worth a shot to capture something...  It came without
> a hard drive, I have Irix 5.3...  I presume it might be supported.

crimson is supported up to 6.2. my release of choice was 5.3XFS.
they aren't quite VME. if memory serves, slots to the left of the
IO are MPBUS, those on the right are VME. same connector, different
wiring. 6.5 requires IP19 (Challenge/Onyx) or higher, and almost
didn't happen for IP20, someone checked in some last-minute kluge.

> Of course, that all presumes I can make room for it in the basement
> and unplug the damn washing machine (the only 20A outlet I have down
> there).

you won't need anywhere near 20A unless you fill the graphics side of
the backplane (for instance, a nice 10-span VGXT).