IBM 608

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The IBM 608 Transistor Calculator, a plugboard-programmable unit, was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the world's first all-transistorized calculator to be manufactured for the commercial market.[1][2]:34 Announced in April 1955,[3][4] it was released in December 1957. The 608 was withdrawn from marketing in April 1959.[3]


The chief designer of the circuits used in the IBM 608 was Robert A. Henle, who later oversaw the development of emitter-coupled logic (ECL) class of circuits.[2]:59 The development of the 608 was preceded by the prototyping of an experimental all-transistor version of the 604. Although this was built and demonstrated in October 1954, it was not commercialized.[2]:50

To spur the adoption of transistor technology, shortly before the first IBM 608 shipped, Tom Watson directed that a date be set after which no new vacuum-tube-based products would be released.[5] This decision constrained IBM product managers, who otherwise had the latitude to select components for their products, to make the move to transistors. As a result, the successor to the IBM 650 used transistors, and it became the IBM 7070—the company's first transistorized stored-program computer.[2]:50

It was similar in nature of operation to the vacuum-tube IBM 604, which had been introduced a decade earlier.[2]:34 Although the 608 outpaced its immediate predecessor, the IBM 607 by a factor of 2.5,[3] it was soon rendered obsolete by newer IBM products and only a few dozen were ever delivered.[2]:48[6]


The 608 contained more than 3,000 germanium transistors.[2]:50 The use of transistors was a significant departure from the previous IBM calculators of this line. The 608 also used magnetic core memory, but was still programmed using a control panel.[7] The main memory of the 608 could store 40 nine-digit numbers, and it had an 18-digit accumulator.[7] In raw speed terms, it could perform 4,500 additions per second, it could multiply two nine-digit numbers, yielding an 18-digit result in 11 milliseconds, and it could divide an 18-digit number by a nine-digit number to produce the nine-digit quotient in 13 milliseconds.[3] The 608 could handle 80 program steps.[7]

The 608 was supplied with a type 535 card reader/punch which had its own control plugboard.

See also[edit]


  1. ^ Bashe, Charles J.; et al. (1986). IBM's Early Computers. MIT. p. 386.
  2. ^ a b c d e f g Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and early 370 systems. MIT Press. ISBN 0-262-16123-0.
  3. ^ a b c d IBM Archives: IBM 608 calculator
  4. ^ Weik, Martin H. (1955). A survey of domestic electronic digital computing systems. Aberdeen Proving Ground, Md. pp. 61–62.
  5. ^ Bashe 1986, p. 387
  6. ^ Bashe 1986, p. 464
  7. ^ a b c Frank da Cruz, The IBM 608 Calculator, Columbia University Computing History

External links[edit]