The Pilot ACE computer was one of the first computers built in the United Kingdom, running its first program on 10th May 1950. It was a preliminary version of the ACE computer, designed by Alan Turing while he worked at the National Physical Laboratory (NPL), who left the NPL before it was completed. It was a general-purpose, stored-program computer, similar to the Manchester Mark I and EDSAC computers of the time. Initially built as a prototype, it was quickly realised that the computer was a useable machine, and was upgraded and was operational until May 1955. It was then donated to the Science Museum in London, where it still is today.

The computer used around 800 valves (vacuum tubes) and its memory consisted of mercury delay lines which originally stored 128 words of 32 bits each. This was later expanded in size. It ran at a clock rate of 1 megahertz, which was very fast for the time.

This item in our collection is one of the mercury delay lines from the Pilot ACE. Mercury delay lines were used as a form of memory storage in some of the earliest computers after the technology had been developed for radar during the Second World War. They worked by converting data bits (ones and zeros) into sound waves, transmitting them acoustically, then converting them back into bits. They circulated indefinitely unless changed by the computer. Mercury was used for a number of factors including the high speed of sound in the element meant that the time it took for pulses to travel the length of the delay line was less than it would have been in slower mediums.

Manufacturer: National Physical Laboratory (NPL)
Date: 1950

This exhibit has a reference ID of CH76431. Please quote this reference ID in any communication with the Centre for Computing History.

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