SPACEWAR! Switch Boxes for a PDP-12

Anders Sandahl anders at
Sun Sep 23 12:51:15 CDT 2018

> Date: Sun, 23 Sep 2018 10:46:48 -0400
> From: Michael Thompson <michael.99.thompson at>
> To: cctech <cctech at>
> Subject: SPACEWAR! Switch Boxes for a PDP-12
> Message-ID:
> 	<CAH1BU=_4OVdEjGgMMcbyLZS9-aDCXp0sZxh1SiEJrtsuWu96Pw at>
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> Visitors to the RICM like to play SPACEWAR! in the PDP-12. Unfortunately
> using the console switches is uncomfortable, not intuitive, and is tough
> on
> the switches. We would like to recreate the switch boxes used on the PDP-1
> to make playing a better experience.
> We modified the source
> <>
> from D.E. WREGE
> <;fn=images/jby/jbyos8.tu56;to=ascii;blk=510,131,0;plain=1>
> to use the LINC SXL instruction to read the PDP-12 GPIO signals, and
> prototyped two switch boxes using recycled toggle switches. This works
> great, so now we need to make better switch boxes.
> This CHM article shows what we want to recreate.
> <>
> This article shows a sketch of the switch boxes.
> <>
> A generous donor made these boxes for us.
> <>
> The lever switches are turning our to be difficult to find at a reasonable
> price. We found some NOS SwitchCraft lever switches that looked like the
> sketch and the PDP-1 pictures and were a reasonable price, but our order
> was rejected because they only had one in stock. eBay has Mossman and
> SwitchCraft, but they are either very expensive (more than $50 each), or
> they only have one available.
> The switches that we are looking for need to be SPDT, three-position,
> non-locking, center off. (If the switches have more than one pole we can
> remove the extra poles to keep the operational force low.) Before we cave
> in and buy some modern C&K toggle switches, does anyone have a source for
> Mossman or SwitchCraft switches at a reasonable price?
> --
> Michael Thompson


I did just what you did for being able to play Spacewar! on my PDP-8a (I
have KK8E with EAE, VC8E and the DK8E real time clock). But since the
frontpanel doesn't have proper switches for the switch register I had to
build game hand controls.

I built them just like those that can be spotted in the video from CHM: but smaller.

I just used ordinary arcade style buttons and connected them to the
digital inputs on the DKC8A board and modified the source code for that.

Those hand controls have two switches for rotate left/right, one for fire
and one for acceleration. The last one is for hyper speed but that is
triggered by pressing left/right switches at the same time. I intended to
fix this so it should be triggered by the last button but never came to

Unfortunately I haven't written on my page on
this yet...


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