Pilot ACE

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The Pilot ACE was one of the first computers built in the United Kingdom, at the National Physical Laboratory (NPL) in the late 1940s.

It was a preliminary version of the full ACE, which had been designed by Alan Turing. After Turing left NPL (in part because he was disillusioned by the lack of progress on building the ACE) James H. Wilkinson took over the project, Harry Huskey helped with the design. The Pilot ACE ran its first program on May 10, 1950 and was demonstrated to the press in December 1950.

Although originally intended as a prototype, it became clear that the machine was a potentially very useful resource, especially given the lack of other computing devices at the time. After some upgrades to make operational use practical, it was into service in late 1951, and saw considerable operational service over the next several years.

It had approximately 800 vacuum tubes, and used mercury delay lines for its main memory. The original size of the latter was 128 32-bit words, but that was later expanded to 352 words; a 4096-word drum memory was added in 1954. Its basic clock rate, 1 megahertz, was the fastest of the early British computers. The time to execute instructions was highly dependent of where they were in memory (due to the use of delay line memory). An addition could take anywhere from 64 microseconds to 1024 microseconds.

The machine was so successful that a commercial version of it, named the DEUCE, was constructed and sold by the English Electric Company.

The Pilot ACE was shut down in May, 1955, and was given to the Science Museum, where it remains today.

[edit] Further reading

Simon H. Lavington, Early British Computers: The Story of Vintage Computers and The People Who Built Them (Manchester University Press, 1980)
David M. Yates, Turing's Legacy: A History of Computing at the National Physical Laboratory, 1945–1995 (Science Museum, London, 1997, ISBN 0-901805-94-7)

[edit] References

James H. Wilkinson, Turing's Work at the National Physical Laboratory and the Construction of Pilot ACE, DEUCE and ACE (in Nicholas Metropolis, J. Howlett, Gian-Carlo Rota, (editors), A History of Computing in the Twentieth Century, Academic Press, New York, 1980)
Martin Campbell-Kelly, Programming the Pilot ACE (in IEEE Annals of the History of Computing, Vol. 3 (No. 2), 1981, pp. 133–162)
B. Jack Copeland (editor), Alan Turing's Automatic Computing Engine. Oxford University Press, 2005 (ISBN 0-19-856593-3)