SPACEWAR! Switch Boxes for a PDP-12

Eric Smith spacewar at
Mon Sep 24 13:26:57 CDT 2018

On Mon, Sep 24, 2018 at 11:23 AM, Robert Feldman via cctalk <
cctalk at> wrote:

> >that is what the PDP-1 at CHM has been using for over 10 years

Ken Sumrall built the Spacewar control boxes used at the museum, with some
suggestions from me. We originally intended these to be temporary, and to
build nicer control boxes later. Since they were intended to be used by
restoration team members, and possibly museum guests, we wanted them to be
reliable rather than authentic, and specifically did NOT want these
temporary boxes to themselves become historical artifacts. We chose
inexpensive but robust arcade pushbuttons. They can take a beating, and in
the event that the microswitch does break or wear out, it can easily be
replaced, though the complete button assembly with microswitch is not
expensive. The boxes are particle board. We used DE-9 connectors. On the
PDP-1, hyperspace is invoked by the CW and CCW rotate controls being
activated simultaneously, so the hyperspace button is wired via series
diodes to both rotate buttons.

After we built them, Steve Russell pointed out to us that although these
boxes don't look like at all like the originals, they actually are
authentic, in the sense that like the originals, these boxes were quickly
knocked together rather than carefully planned, and are functional rather
than pretty.

We positioned the individual buttons based on the layout used on one of the
Atari coinop games, "Space Duel" IIRC, on the because Atari had done a good
job of laying them out to be easy to use.

I'm not trying to discourage anyone from trying to make replicas of the
original Spacewar control boxes, but aside from some grainy photos and a
brief description, not much detail about them is actually known.

We do not know what controls were used when PDP-1 Spacewar was demonstrated
at the Computer Museum in Boston. We don't think they had the original
control boxes. Possibly they might have just used the PDP-1 console
switches, which is quite inconvenient and increases wear on those
switches.  When we restored the PDP-1, we discovered that some of the
console switches were flaky, and upon inspection, that they appeared to
have been replaced multiple times, with suboptimal craftsmanship.

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