The AN/USQ-17 or Naval Tactical Data System (NTDS) computer referred to in Sperry Rand documents as the Univac M-460, was Seymour Cray's last design for UNIVAC.[1][2] UNIVAC later released a commercial version, the UNIVAC 490 and that system was later upgraded to a multiprocessor configuration as the 494.

The machine was the size and shape of a refrigerator, about four feet high (roughly 1.20 meters), with a hinged lid for access. However, shortly after completing the prototype design Cray left to join Control Data Corporation. When the Navy awarded Sperry Rand a US$50 million contract to build the AN/USQ-17, Univac engineers redesigned the entire machine from scratch using silicon transistors (retaining the instruction set so that programs developed for the original machine would still run on the new one).[3]

As part of the redesign it was decided to improve access, and the second version was designed to stand upright, like an old fashioned double-door refrigerator, about six feet tall (roughly 1.80 m). This new design was designated the AN/USQ-20.

Instructions were represented as 30-bit words, in the following format:

  f   6 bits   function code 
  j   3 bits   jump condition designator 
  k   3 bits   partial word designator 
  b   3 bits   which index register to use 
  y  15 bits   operand address in memory

Numbers were represented as 30-bit words, this allowed for five 6-bit alphanumeric characters per word.

The main memory was 32,768 = 32K words of core memory.

The available processor registers were:

  • One 30-bit accumulator (A).
  • One 30-bit Q register (combined with A to give a total of 60 bits for the result of multiplication or the dividend in division).
  • Seven 15-bit index registers (B1–B7).

The instruction format defined for the AN/USQ-17 marked the beginning of an instruction set which would be carried on, with many changes along the way, into later UNIVAC computers including the UNIVAC 1100/2200 series which is still in use today.

See also


  1. ^ Marshall William McMurran (11 December 2008). ACHIEVING ACCURACY: A Legacy of Computers and Missiles. Xlibris Corporation. pp. 142–. ISBN 978-1-4628-1065-9.
  2. ^ James A. Treadway (July 2005). Hard Charger!: The Story of the USS Biddle (DLG-34). iUniverse. pp. 107–. ISBN 978-0-595-36009-3.
  3. ^ David L. Boslaugh (16 April 2003). When Computers Went to Sea: The Digitization of the United States Navy. John Wiley & Sons. pp. 165–. ISBN 978-0-471-47220-9.

External links

  • The Univac M-460 Computer – Paper by J. E. Thornton, M. Macaulay, and D. H. Toth, Remington Rand Univac Division of Sperry Rand (on-line version from Ed Thelen's Antique Computer Home Page)

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