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PDP-1, CRT, TTY and processor rack [1]

PDP-1, (Programmed Data Processor-1)
the first computer in DEC's Programmed Data Processor series, first launched in 1960, forerunner of the PDP-8 and PDP-11 minicomputers, and the World's first commercial interactive computer used for process control, scientific research, and graphics programming, as well as to pioneer timesharing systems.

Based on the TX-0 and TX-2 computers he had designed at MIT's Lincoln Laboratory, Ben Gurley constructed the PDP-11 in under three–and–a–half months [2]. The PDP-1 had 4K 18-bit words as standard main memory, upgradable to 64K words, and an internal instruction execution rate of 100,000 to 200,000 per second [3]. Signed numbers were represented in ones' complement.


The processor consists of discrete germanium transistor logic in form of System Building Block modules, inserting 25 of them into a 5-1/4 inch section of a custom 19-inch rack.


System Building Block 1103 - hex-inverter card [4]


In the early 60s, Edward Fredkin, while affiliated with BBN, wrote the first PDP-1 assembler called FRAP (Fredkin’s Assembly Program) [5].

Fredkin working on pdp1.jpg

Ed Fredkin working on PDP-1 (1960 ca.) [6]

PDP-1 Chess

As told by Alan Kotok at the PDP-1 Celebration Event Lecture, May 15, 2006 [7], PDP-1 Chess, a apparently strong new chess program developed at BBN or elsewhere, was a hoax. Kotok, at that time in the early 60s student at MIT and PDP-1 programmer, was member of the Tech Model Railroad Club as well as member of the chess group around John McCarthy, and already co-author of Kotok-McCarthy for the IBM 7090. He and some of his colleagues had established a network, a TTY connection between the PDP-1 and the TX 0 in an adjoining room, where some of the better MIT chess players "simulated" PDP-1 Chess with a chess board at the TTY console, playing a game versus some testers with McCarthy involved. The "cheat" was finally noticed, when later during the game both board positions somehow became out of sync.


In 1961/62, Steve Russell developed Spacewar!, one of the first interactive video games, after Alan Kotok obtained some sine and cosine routines from DEC [8].

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