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IAS machine

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IAS machine
The IAS machine on display at the Smithsonian Institution
DeveloperJohn von Neumann
ManufacturerInstitute for Advanced Study (IAS)
Release dateJune 10, 1952; 72 years ago (1952-06-10)
CPU1,700 vacuum tubes
Memory1,024 words (5.1 kilobytes) (Williams tubes)
Mass1,000 pounds (450 kg)
James Pomerene working on the IAS machine

The IAS machine was the first electronic computer built at the Institute for Advanced Study (IAS) in Princeton, New Jersey. It is sometimes called the von Neumann machine, since the paper describing its design was edited by John von Neumann, a mathematics professor at both Princeton University and IAS. The computer was built under his direction, starting in 1946 and finished in 1951.[1] The general organization is called von Neumann architecture, even though it was both conceived and implemented by others.[2] The computer is in the collection of the Smithsonian National Museum of American History but is not currently on display.[3]


J. Robert Oppenheimer and John von Neumann in front of the IAS machine

Julian Bigelow was hired as chief engineer in May 1946.[4] Hewitt Crane, Herman Goldstine, Gerald Estrin, Arthur Burks, George W. Brown and Willis Ware also worked on the project.[5] The machine was in limited operation in the summer of 1951 and fully operational on June 10, 1952.[6][7][8] It was in operation until July 15, 1958.[9]


The IAS machine was a binary computer with a 40-bit word, storing two 20-bit instructions in each word. The memory was 1,024 words (5 kilobytes in modern terminology). Negative numbers were represented in two's complement format. It had two general-purpose registers available: the Accumulator (AC) and Multiplier/Quotient (MQ). It used 1,700 vacuum tubes (triode types: 6J6, 5670, 5687, a few diodes: type 6AL5, 150 pentodes to drive the memory CRTs, and 41 CRTs (type: 5CP1A): 40 used as Williams tubes for memory plus one more to monitor the state of a memory tube).[10] The memory was originally designed for about 2,300 RCA Selectron vacuum tubes. Problems with the development of these complex tubes forced the switch to Williams tubes.

It weighed about 1,000 pounds (450 kg).[11]

It was an asynchronous machine, meaning that there was no central clock regulating the timing of the instructions. One instruction started executing when the previous one finished. The addition time was 62 microseconds and the multiplication time was 713 microseconds.

Although some claim the IAS machine was the first design to mix programs and data in a single memory, that had been implemented four years earlier by the 1948 Manchester Baby.[12] The Soviet MESM also became operational prior to the IAS machine.

Von Neumann showed how the combination of instructions and data in one memory could be used to implement loops, by modifying branch instructions when a loop was completed, for example. The requirement that instructions, data and input/output be accessed via the same bus later came to be known as the Von Neumann bottleneck.

IAS machine derivatives[edit]

Plans for the IAS machine were widely distributed to any schools, businesses, or companies interested in computing machines, resulting in the construction of several derivative computers referred to as "IAS machines", although they were not software compatible.[5]

Some of these "IAS machines" were:[13]

See also[edit]


  1. ^ "The IAS Computer, 1952". National Museum of American History, Smithsonian Institution.
  2. ^ Deepali A.Godse; Atul P.Godse (2010). Computer Organization. Technical Publications. pp. 3–9. ISBN 978-81-8431-772-5.
  3. ^ Smithsonian IAS webpage
  4. ^ John Markoff (February 22, 2003). "Julian Bigelow, 89, Mathematician and Computer Pioneer". The New York Times.
  5. ^ a b c "Electronic Computer Project". Institute for Advanced Study. Retrieved May 26, 2011.
  6. ^ Goldstein, Herman (1972). The Computer: From Pascal to von Neumann. Princeton, NJ: Princeton University Press. pp. 317–318. ISBN 0-691-02367-0.
  7. ^ Macrae, Norman (1999). John Von Neumann: The Scientific Genius who Pioneered the Modern Computer, Game Theory, Nuclear Deterrence, and Much More. American Mathematical Soc. p. 310. ISBN 9780821826768.
  8. ^ "Automatic Computing Machinery: News - Institute for Advanced Study". Mathematics of Computation. 6 (40): 245–246. Oct 1952. doi:10.1090/S0025-5718-52-99384-8. ISSN 0025-5718.
  9. ^ Dyson, George (March 2003), "George Dyson at the birth of the computer", TED (Technology Entertainment Design) (Video), TED Conferences, LLC, archived from the original on 2012-03-17, retrieved 2012-03-21
  10. ^ The history and development of the electronic computer project at the Institute for Advanced Study. Ware. 1953
  11. ^ Weik, Martin H. (December 1955). "IAS". ed-thelen.org. A Survey of Domestic Electronic Digital Computing Systems.
  12. ^ "Manchester Baby Computer". Archived from the original on 2012-06-04.
  13. ^ "The IAS computer family scrapbook | 102693640 | Computer History Museum". www.computerhistory.org. 2003. Retrieved 2018-05-23.
  14. ^
  15. ^ "Commercially Available General-Purpose Electronic Digital Computers of Moderate Price: THE CIRCLE COMPUTER".
  16. ^ IAS type machine:
  17. ^ Weik, Martin H. (Dec 1955). "CIRCLE". ed-thelen.org. A Survey of Domestic Electronic Digital Computing Systems.
  18. ^
  19. ^ a b Turing's Cathedral, by George Dyson, 2012, p. 287

Further reading[edit]

External links[edit]