Pilot ACE
Encyclopedia
The Pilot ACE was one of the first computer
s built in the United Kingdom
, at the National Physical Laboratory
(NPL) in the early 1950s.
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 went into service in late 1951, and saw considerable operational service over the next several years. One reason the ACE was so useful is that it was able to perform so-called Floating point arithmetic so useful for scientific calculations. Wilkinson tells the story of how this came to be. The pilot ACE was built without arithmetic hardware, in contrast to other computers at that time, which were built with fixed-point hardware. The ACE started out using fixed-point implemented as software, but it soon became apparent that this was a bad idea because the numbers quickly became either too big or too small to be contained in the computer. It only took a week to write new software so that the ACE could do floating-point arithmetic. After that, James H. Wilkinson's wrote a book on rounding errors in floating-point calculations, which became a best seller.
It had approximately 800 vacuum tube
s, 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.
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s built in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, at the National Physical Laboratory
National Physical Laboratory, UK
The National Physical Laboratory is the national measurement standards laboratory for the United Kingdom, based at Bushy Park in Teddington, London, England. It is the largest applied physics organisation in the UK.-Description:...
(NPL) in the early 1950s.
It was a preliminary version of the full ACE
ACE (computer)
The Automatic Computing Engine was an early electronic stored-program computer design produced by Alan Turing at the invitation of John R. Womersley, superintendent of the Mathematics Division of the National Physical Laboratory . The use of the word Engine was in homage to Charles Babbage and his...
, which had been designed by Alan Turing
Alan Turing
Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
. After Turing left NPL (in part because he was disillusioned by the lack of progress on building the ACE), James H. Wilkinson
James H. Wilkinson
James Hardy Wilkinson was a prominent figure in the field of numerical analysis, a field at the boundary of applied mathematics and computer science particularly useful to physics and engineering.-Early life:...
took over the project, Harry Huskey
Harry Huskey
Harry Douglas Huskey is an American computer designer pioneer.Huskey was born in the Smoky Mountains region of North Carolina and grew up in Idaho. He gained his Master's and then his PhD in 1943 from the Ohio State University on Contributions to the Problem of Geocze...
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 went into service in late 1951, and saw considerable operational service over the next several years. One reason the ACE was so useful is that it was able to perform so-called Floating point arithmetic so useful for scientific calculations. Wilkinson tells the story of how this came to be. The pilot ACE was built without arithmetic hardware, in contrast to other computers at that time, which were built with fixed-point hardware. The ACE started out using fixed-point implemented as software, but it soon became apparent that this was a bad idea because the numbers quickly became either too big or too small to be contained in the computer. It only took a week to write new software so that the ACE could do floating-point arithmetic. After that, James H. Wilkinson's wrote a book on rounding errors in floating-point calculations, which became a best seller.
It had approximately 800 vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s, and used mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
delay lines
Delay line memory
Delay line memory was a form of computer memory used on some of the earliest digital computers. Like many modern forms of electronic computer memory, delay line memory was a refreshable memory, but as opposed to modern random-access memory, delay line memory was serial-access...
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
Drum memory
Drum memory is a magnetic data storage device and was an early form of computer memory widely used in the 1950s and into the 1960s, invented by Gustav Tauschek in 1932 in Austria....
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
English Electric DEUCE
The DEUCE was one of the earliest British commercially available computers, built by English Electric from 1955.It was the production version of the Pilot ACE, itself a cut down version of Alan Turing's ACE....
, was constructed and sold by the English Electric
English Electric
English Electric was a British industrial manufacturer. Founded in 1918, it initially specialised in industrial electric motors and transformers...
Company.
The Pilot ACE was shut down in May, 1955, and was given to the Science Museum
Science Museum (London)
The Science Museum is one of the three major museums on Exhibition Road, South Kensington, London in the Royal Borough of Kensington and Chelsea. It is part of the National Museum of Science and Industry. The museum is a major London tourist attraction....
, where it remains today.
Further reading
- Simon H. Lavington, Early British Computers: The Story of Vintage Computers and The People Who Built Them (Manchester University PressManchester University PressManchester University Press is the university press of the University of Manchester, England and a publisher of academic books and journals. Manchester University Press has developed into an international publisher...
, 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)
External links
- Oral history interview with Donald W. Davies, Charles Babbage InstituteCharles Babbage InstituteThe Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....
, University of Minnesota. Davies describes computer projects at the U.K. National Physical Laboratory, from the 1947 design work of Alan TuringAlan TuringAlan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
to the development of the two ACE computers. Davies discusses a much larger, second ACE, and the decision to contract with English ElectricEnglish ElectricEnglish Electric was a British industrial manufacturer. Founded in 1918, it initially specialised in industrial electric motors and transformers...
Company to build the DEUCEEnglish Electric DEUCEThe DEUCE was one of the earliest British commercially available computers, built by English Electric from 1955.It was the production version of the Pilot ACE, itself a cut down version of Alan Turing's ACE....
-- possibly the first commercially produced computer in Great Britain. - The Pilot ACE at the Science Museum
- How Alan Turing's Pilot ACE changed computing
- The world's first multi-tasking computer