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From: Ethan Dicks <>
Date: Wed Apr 16 13:52:00 2003

--- William Donzelli <> wrote:
> > The systems are two identical DEC PDP-11/70's that seem to date from
> > the early 1980's. There are two CDC 9766 drives... aftermarket
> > supplier - Systems Industries?
> SI made lots of disk products for DECs.

My first 11/750 had an SI9900 on it from the day it was used by the
original owner. My 11/70s also have SI9900s - they are, in their
simplest form, a 5.25"-tall rack-mounted box with cards that talk to
hosts (over MASSBUS for the 11/750 and 11/70; over Qbus or Unibus for
"lesser" machines), and cards that talk to drives (SMD, as far as I've
seen). You can pack several of each kind on their respective sides
of the enclosure. The 11/750 controlled two drives and had a total
of three cards (one host, two drive)

I know they made wads of other, less elaborate, interfaces.

The 11/70s also came with SI-badged tape drives, in 60" Corporate-Cab-
style cabinets.

> At one point I had a somewhat trashed Diablo drive for a PDP-8/E
> RKmumble), with an SI interface board and power supply.

I haven't seen an OMNIBUS SI controller for Diablos, but the
PDP-8/m-based Mass Spectrometer at the Vet School at Ohio State
had a different brand of dual-ported controller - the operator would
switch a drive to face the -8/m that ran the mass spec, collect
samples, then flip the drive to face the -8/m that had the Tektronix
terminals, analyze and print the results.

I'm sorry I never got that machine when they dumped it - two CPUs,
24K of core each (IIRC), two 4014 terminals, a 9-track mag tape,
4 or 5 Diablo model 30s, and a Xebec? dual-ported OMNIBUS disk
controller, all in 4 racks! At least I got to play on it when the
mass spec was being torn down and cleaned. :-)

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Received on Wed Apr 16 2003 - 13:52:00 BST

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