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IAS machine

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Title: IAS machine  
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Subject: IAS architecture computers, ORACLE (computer), MISTIC, Minimal instruction set computer, Von Neumann architecture
Collection: Ias Architecture Computers, Vacuum Tube Computers
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IAS machine

The IAS machine at the National Museum of American History

The IAS machine was the first electronic [2]


  • History 1
  • Description 2
  • IAS machine derivatives 3
  • See also 4
  • References 5
  • Further reading 6
  • External links 7


Julian Bigelow was hired as chief engineer in May 1946.[3] Hewitt Crane, Herman Goldstine, Gerald Estrin, Arthur Burks and Willis Ware also worked on the project.[4] The machine was in limited operation in the summer of 1951 and fully operational on June 10, 1952.[5]

It was in operation until July 15, 1958.[6]


The IAS machine was a binary computer with a 40-bit word, storing two 20-bit instructions in each word. The memory was 1024 words (5.1 kilobytes). Negative numbers were represented in "two's complement" format. It had two general-purpose registers available: the Accumulator (AC) and Multiplier/Quotient (MQ).

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 Small Scale Experimental Machine.[7] Also MESM became operational prior to 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 resultant demand that instructions and data be placed on the same memory later came to be known as the Von Neumann Bottleneck.

The memory was originally designed for about 2300 RCA Selectron vacuum tubes. Problems with the development of these complex tubes forced the switch to Williams tubes.

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.

IAS machine derivatives

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 in the modern sense.[4]

Some of these "IAS machines" were:

See also


  1. ^ "The IAS Computer, 1952".  
  2. ^ D. A.Godse; A. P.Godse (2010). Computer Organization. Technical Publications. pp. 3–9.  
  3. ^  
  4. ^ a b c "Electronic Computer Project".  
  5. ^ Goldstein, Herman (1972). The Computer: From Pascal to von Neumann. Princeton, NJ: Princeton University Press. p. 318.  
  6. ^ Dyson, George (March 2003), "George Dyson at the birth of the computer", TED (Technology Entertainment Design) (Video), TED Conferences, LLC, retrieved 2012-03-21 
  7. ^ "Manchester Baby Computer". 
  8. ^ a b Turing's Cathedral, by George Dyson, 2012, p. 287

Further reading

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