Space War Simulator


UPDATE December 2015: I was contacted by a user on the MESS emulator forum by the nickname Stiletto that there is now a way to get Space War running on MAME 0.167 with a few tweaks and adjustments. The details are ratgher complex so I'll post the link here to allow any readers to follow the original instructions rather than try to re-write and make a mistake here.

Space War on PDP1?

UPDATE 2015: I was noticing several visitors to my site asking me why the PDP simulator was no longer working, despite updating this page a coule of years ago and I could not understand why the emails kept coming in. As it turns out, WIRED Magazine editor Chris Kohler mentioned both my website as well as the original M.E.S.S. instructions I had posted years ago in his book Retro Gaming Hacks. Here is a link to the section in Chris'es excellent book where my site is mentioned. Alas as explained below in my 2012 update, those instructions do not work fully in newer versions of M.E.S.S. But many thanks to Chris for the shout-out nonetheless!

UPDATE 2012: due to changes in the M.E.S.S. program the instructions below no longer work. However the PDP version of Space War is playable through a Java-enabled emulator at


Original instructions (in case some day M.E.S.S. runs like it used to when these instructions were written) are as follows:

To run Space War you first need the Multiple Emulator Super System (M.E.S.S.) from (freeware)

This program runs very similar to MAME, with a similar folder structure. However, none of that needs to be configured. All you need to do is launch the program by means of double clicking messgui.exe

Next, download this .zip file which contains a useful readme.txt from the creator of the file, Raphael Nabet, as well as the spacewar.rim file that M.E.S.S. requires.

In M.E.S.S, navigate down the list to the PDP-1 entry and double click (it is important you double click PDP-1).

A largely black screen will fill your monitor showing a number of controls and a familiar File menu along the top.

Click Devices > Punched Tape #1 > Mount… and navigate to the spacewar.rim file.

You would expect the game to begin, however, you are really only half way there. The file is mounted but has not yet been “fed” into the virtual PDP-1. You need to hit Ctrl-Enter in order to fed the program into the machine. You will know the game has begun when you see the blinking light indicators showing the load is in progress. These blinking lights can be seen on a real PDP machine here.

When completed, Space War begins!

There are details in the Spacewar readme.txt on how to control the two ships. For simplicity I have copied that section of the readme.txt here so you can start playing right away but I would urge you to read the entire file to be able to configure various game settings.

Control the ship with the default MESS key mapping A, S, D, F and Z keys for player 1, and to the arrow and / keys for player 2.

Many thanks to Raphael Nabet and the people behind M.E.S.S. for making this fantastic emulation possible.