English Electric DEUCE

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The DEUCE (Digital Electronic Universal Computing Engine) was one of the earliest British commercially available computers, built by English Electric in the early 1950s.

It was a productionized version of the Pilot ACE, itself a cut down version of Alan Turing's ACE. Pilot ACE had 1450 thermionic valves, and used mercury delay lines for its main memory; each of the 12 delay lines could store 32 instructions or data words of 32 bits. It shared the 1 megahertz clock rate of the Pilot ACE. Although The DEUCE also had a magnetic drum for storage, its reliance on delay line memory rendered it obsolete when compared with equivalent conteporaries such as the Manchester Mark I.

Programming the DEUCE involved added complication, as each instruction had to wait its turn in the delay line – the order of instructions greatly affected performance. Reading data from a card reader also had to be done in real-time – each row had to be read as it passed the read heads, and no stopping!

The front panel of the DEUCE featured a CRT display which showed the current contents of store. The first machines were delivered in the spring of 1955; in late 1955 a DEUCE 2 improved model appeared, to be followed by a DEUCE 2A in 1957.

A total of 31 DEUCE machines were sold between 1955 and 1964.