Spacewar! On PDP-11 Restoration

If you want to play the original Spacewar! but you don’t have a PDP-1 nearby, then you’re in luck — assuming you have a PDP-11, that is. [Mattis Lind] has successfully restored a PDP-11 port of the game from PDF scans of the source code, which was thought to have been lost to the trash bins of DECUS (Digital Equipment Computer Users’ Society). Fortunately, [Mattis] learned that [Bill Seiler], one of the original authors, had saved a printout of the assembly language. Using a combination of OCR and manual transcription to retrieve the code, [Mattis] took a deep dive into cleaning up the errors and solving a whole lot of system library and linking issues. Adding to the difficulty is that his PDP-11 is slightly different from the one used in 1974 when this port was written.

The project was not all software — [Mattis] also needed to make a pair of joysticks, which he made from a handful of items found on AliExpress. As you can see in the video below, he indeed got it all working. [Mattis] is no stranger to the PDP-11 world. We wrote about his PDP-11 restoration project back in 2015, a quest that took over 18 months.

9 thoughts on “Spacewar! On PDP-11 Restoration

      1. No, I’ve seen the Vetrex before. Can’t recall if I’ve actually played one or not. But the one I linked to above was the one– though I don’t know if there was a difference between a “German” on and an “American” one (presuming there even is a difference, simply because the website is german, *.de). I remember a friend and I stumbled across it set up at the train station and it was very interesting and unique at the time. But expensive, requiring $0.50 each for us to play it together. So we didn’t play it more than a few times.

  1. I remember playing this on a mainframe at UBC back in the mid 70’s. Would have been a variant of it of course, as I’m pretty sure it wasn’t a DEC machine. Recall having to use a paper tape to do the initial boot. Was a huge machine in it’s own air con room.

  2. We had a DEC GT40 (PDP-11/05, VT40) that would bootstrap from the host PDP-11/40 at Auburn University, Electrical Engineering Department. Lunar Lander and SpaceWar were very popular ways to pass the time. An A/D module was used for the two ‘controllers’ to play SpaceWar and a lightpen was used for Lunar Lander. This was late 1970s. The PDP 11/40 had Tektronix displays (all serial connections back then, DH11’s) and various games too were played on them. Golf was the most popular. The PDP-11/40 ran RSTS/e, an amazing O/S. Great job on the work Sir!

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