The English Electric KDF9 was an advanced and successful transistorised computer, in use from 1963. There is some information elsewhere on the Web about it. It is remarkable in being possibly the first "zero-address" or stack based computer to be delivered, although Burroughs in the USA produced another at about the same time. The use of a stack simplified certain operations and facilitated the creation of computer languages like Algol.

Click to enlarge I possess a number of logic cards from the KDF9. The top image shows a 'flip flop' card in side view, plus an oblique view of the front panel: click on the thumbnail image of the card to see a larger version (100KBytes). The card is made of brown paxolin, 8 inches by 6 and 1/4 inches with a 32-way edge connector at the rear. It has a small red plastic handle marked FF2 recessed into the front edge, which also has 9 test points. This particular card bears eight 2N269 transistors, made by the British company Associated Transistors, which was part-owned by English Electric.

KDF9 magnetic logic It also has eight magnetic logic units, one of which is shown in the lower image. Unlike the EMIDEC 1100 described elsewhere on my site, these units appear to be all identical, and are simpler, with only six connections. This card is marked on the printed circuit side "FOR DEVELOPMENT ONLY".

Interestingly, the Newcastle University computer science site also shows a similar flip flop card. However, their example uses GEC transistors (I can recognise their unique appearance), and the magnetic devices appear to be potted in plastic. Perhaps they have the production version and mine were developmental.

Incidentally, a KDF9 was in use at Imperial College, London University, when I attended there, and I believe that although I did not use it myself, I did get a colleague to run some jobs on it to produce line-printer art!