A user works at an IMLAC PDS-4. Rutherford Appleton Laboratory, Oxfordshire, Unites Kingdom.

The IMLAC PDS-4 was an updated version of the PDS-1 which was originally released in 1970. The PDS-1 is a graphical display system that was used in the 1970s. It included A CRT monitor (vector display), control panel, and desk pedastal which contained a 16-bit minicomputer, core memory and display processor.

The PDS-1 while low cost for its time compared to other similar computers was hugely expensive by today’s standards. The base model would set you back about $8,300 which is over $54,000 in today’s dollars. It was used to develop one of the first hypertext systems and was also used as a component in larger systems including a newspaper layout and typesetting system. But it was an early game development and gaming system too. Spacewar! started out as a demo on the PDP-1 and and later expanded for the PDS-1. The first online multiplayer computer game, Mazewar, was also first created on a couple of PDS-1s. Perhaps most interestingly, Frogger started life as a game called Freeway that was developed on a PDS-1 as a psychology experiment related to the study of short-term memory. It was commercialized by Konami and titled “Highway Crossing Frog” before Sega decided Frogger was a better name.

The PDS-4 was very similar to the PDS-1 but it was twice as fast and able to display twice as many lines of text without flicker. Like the PDS-1, the PDS-4 was built to order and not mass produced. Approximately 700 PDS-4s were sold in the U.S. by 1977.


    • Link to the photo as I found it is here. This was found on Tumblr but no original source was given.



2 Responses to IMLAC PDS-4

  1. I think Spacewar was first on the PDP-1. Later ported to an Imlac.

    • You’re right. It was first written as a demo for the PDP-1 and then expanded upon for the IMLAC. I corrected the text above.