PDP-11/70 rescued!

From: Ethan Dicks <erd_at_infinet.com>
Date: Fri Oct 23 08:15:43 1998

 
The Computer Quonset Hut has its first aquisition - a pair of PDP-11/70's
with peripherals. A former employer of mine managed to be in the right place
and the right time, consulting for the same guys he used to consult with
in the 1970's, and we nabbed the machines the week they were decommissioned.
My biggest disappointment is that the CPUs have the corporate front panel,
not the programmer's front panel. Anyone have a spare front panel they
want to trade? ;-)

The haul includes:

        2 PDP-11/70 CPUs w/4Mb MOS memory (lots of 16K DRAMs)
        3 System Industries magtape drives (StorageTek 1150's inside?)
        5 System Industries SI9900/SI9900R interfaces (SMD<->Massbus)
        7 Fujitsu Eagle (470Mb) SMD disks (minus a few cables).

Given the naming scheme (COLA, COLB, COLC, COLD, COLE) that they used to
employ (Columbus A...), I suspect that I have all the disks and two of the
remaining CPUs out of a once larger installation.

This is *way* more equipment than I need. I'm not cramped for room yet
(the Hut is 32'x48'), but I can see it happening down the road. If anyone
has an interest in SI hardware, I have lots of it. Please contact me
if you are interested in some kind of swap arrangement. I might also
be amenable to trading spares, not just entire racks.

While I don't regret rescuing this stuff, I have no clue how long it will be
until I could ever power this stuff on. The Hut has its own 60 Amp feed
seperate from the house, but 110/220, no three-phase power. I suppose I
could purchase/rig-up a 220V<->3Ph mechanical converter, but I'd be more
likely to do my own load balancing on the two phases that I have and bypass
the internal DEC power sequencers. Does anyone out there have any experience
with powering up an 11/70 in a non-commercial environment?

Fortunately, I have smaller, cheaper-to-run PDP-11's for day-to-day stuff.
I'd hate to pay for this thing 24x7. The cabinet is labelled at 24A/Ph,
making me think that one CPU wants 8000W of power, but that must be a full
boat with some added safety margin. In any case, at roughly $0.08/kWH,
$15/day to power on, or $450/month, cooling notwithstanding. I wouldn't have
enough juice in the Hut to run it anyway, not if that load is typical.

My goal over the next couple of years is to fix this place up enough to
set up a by-appointment-only museum. Maybe I can get something going by
mid-next year. For the curious, my collection leans towards 1970's micros
and DEC hardware with a liberal sprinkling of 68K.

-ethan

P.S. ISTR that PDP-11/70's and VAX-11/750's use the same hex-height 39-bit
ECC memory boards. Is this true? I know that 750's had 256K and 1Mb
boards (and eventually 4Mb boards), but every jump up required a new
memory controller (and backplane wires ;-) What's the scoop on the 11/70?
Received on Fri Oct 23 1998 - 08:15:43 BST