System Industries QBus board

From: Ethan Dicks <>
Date: Tue Apr 9 23:52:12 2002

--- Doc Shipley <> wrote:
> Unidentified Quad-Height Board:
> System Industries
> 9901-6082-a
> Date Code 621

I think I have one or two of these. Never powered them on. Got them
in a pile of spare SI9900 parts over 5 years ago.

> It has 2 40-pin connectors

The connector to the 9900 is a pair of BC08 cables (40-pin ribbon

I have never used a 9900 with a MicroVAX, but we used to use one
every day on our 11/750 with a Massbus adapter. There was an SI-
specific cable set that went from the 11/750 backplane to a pair of
40-pin connectors that did not resemble the 3-tier Massbus connector.
The two 11/70s I got a couple of years ago both came with 9900 adapters.
I would have to poke around with a flashlight to report how they attach.

The arrangement was this...

Some sort of host board -> SI9900 -> one or more SMD drives.

You could plug multiple hosts into one SI9900, but we never did. You
could plug multiple disk boards into it, too, and we did do that, IIRC.

The SI9900 itself is a 5"-tall rackable box with a PSU and two bays for
cards. They stacked on the left and on the right - one for host cards
(with a pair of 40-pin cables going to each host) and one for drive
cards. It's been so long since I've been in one that I forget if
the drive cards supported multiple drives per card. Ours had a 160MB
Fujitsu drive and an Eagle; I don't recall how many drive cards were
in the 9900.

>From the standpoint of the 11/750, it saw two RM03s and a strange RM05.
We didn't have to patch the OS to access the 160MB Fuji as two 67MB
devices, but we did have to wait on SI to upgrade VMS until they released
a patch for the DRDRIVER (IIRC) to add/modify an entry for our oversized
RM05 (~400MB).

Obviously, the SI9900 works with the PDP-11/70, but I have no experience
with it. I do not know what device the Qbus board resembles. If you
don't have the 9900 itself, that card isn't going to do you much good.

I don't know why we went with the SI9900, but it would have been c. 1983
or 1984. It was probably the fastest, cheapest way to throw some disk
on our *new* 11/750 (BT0000354) About the same time, an RA81 was $26,000
plus the cost of the UDA-50. A Unibus SMD interface might have been
cheaper, but not as fast.


Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax
Received on Tue Apr 09 2002 - 23:52:12 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:34:30 BST