Inquiry on System Industries Qbus SCSI

tiggerlasv at tiggerlasv at
Sun Apr 27 00:05:05 CDT 2008

I had put a few feelers out there a few months ago,
but was met with silence.  It was ominous.
You could hear crickets chirping.   ;-)

One company (Scottish Data Systems) may or may not
have the manual; I offered them like $50 + S/H for a real copy,
or $40 for an e-mailed copy, but never heard back from them.

I may have another source for the manual,
but I won't know for a few more weeks.

I have not been able to get a FULL description
of this board's capabilities.

I do know that at least half of the board
functions as a SCSI tape controller, with
TMSCP emulation, and have been able to get
that part of the functionality partially working.

Here is what I have so far:

SW-2 is a 10-position dip switch at the back of the board.

The switch settings are backwards from the norm.
Thus, OFF/OPEN switches are a logical "1".

1 = OPEN = OFF

Here is the bit decoding:

If you copy & paste this into a fixed font (not true type),
this should line up properly.  I use Notepad in Windoze.

SWITCH  10     9  8  7      6  5  4     3  X  2     1
BIT     1      4  2  1      4  2  1     4  2  1     4

        O      O  C  C      O  C  O     C  -  C     C

        7         4            5           0        0

Note the missing bit in the address selection,
which correlates to the TMSCP addressing scheme.

The 50-pin connector towards the front of the controller
appears to be single-ended SCSI.

The connector set further back is probably
a differential SCSI interface, based on the DS75176's
I see directly behind the connector.

There are interrupt select jumpers at the back;
the jumper closest to the edge is BR4.

There is also a BEVENT jumper near the
back, center of the board.

I have no idea what the function of SW1 is.

There is a row of jumpers along the right edge,
which may be LUN selection.

I'm guessing the jumpers at the front of the board
are terminator / terminator power jumpers.

So far, I've been able to get the controller address set,
and have attached an Exabyte 8200 tape drive to it.

When I attempt to boot a tape, it does seem to send
commands to the tape drive, and the tape starts to seek.
After several seconds however, the processor halts.

If I boot RSTS/E, it hangs during INIT before
ever getting to a prompt.

Clearly, further poking around is required.

If anyone has any insight, it would be appreciated,
especially the current position of any of the jumpers
on your board, and settings for SW1.

I will keep you posted. . .


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