SPACEWAR! Switch Boxes for a PDP-12

Anders Sandahl anders at
Tue Sep 25 12:25:10 CDT 2018

> Date: Mon, 24 Sep 2018 12:26:57 -0600
> From: Eric Smith <spacewar at>
> To: "General Discussion: On-Topic and Off-Topic Posts"
> 	<cctalk at>
> Subject: Re: SPACEWAR! Switch Boxes for a PDP-12
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> 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.

I like the ideas with the diodes for hyperspace, I'll steal that right away!

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