Sparcstation SCSI connections

[Chris Johnson]

I've been having some goofy problems with SCSI errors when I connect up an
external device along with an Ancot SCSI-bus analyzer.  I know all about
the rules for lengths and terminations for SCSI.

But what I want to know is, just what is Sun doing on the inside of the
Sparcstation?  After all, they've got the external SCSI connector, and two
internal SCSI connectors.  Which of those are terminated?  Just the
external?  All three?  And correspondingly, which of the two internal hard
disks I have should be terminated?  Both?  Neither?  Left?  Right?

A schematic of the CPU board would answer all my questions.  From just
looking at the thing, it looks like there is just one set of terminators
soldered to the board, which would lead me to think neither of the
internal drives should be terminated.  Except Sun ships the normal one
disk terminated.  Which suggests the second disk should not be terminated,
if the internal disk is providing the "host end" SCSI bus termination.
Unless the internal SCSI sockets have their own driver IC's separate from
the external SCSI connector.  Which also might be true, given that they
are on the opposite side of the CPU board, and SCSI stub lengths are
supposed to be less than 10cm, and the board is quite a bit wider than
that.

Aaaaiieeeee!  Does anyone know the correct answer?

   ...Chris Johnson          chris at c2s.mn.org   ..uunet!bungia!com50!chris
 Com Squared Systems, Inc.   St. Paul, MN USA   +1 612 452 9522