IBM 701

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IBM 701
Manufacturer: International Business Machines
Year Announced: April, 1952
Year Design Started: February, 1951
Year First Shipped: December, 1952
Year Discontinued: June, 1954
Form Factor: mainframe
Word Size: 18 or 36 bits
Logic Type: vacuum tubes
Clock Speed: 60 μsec (basic add instruction)

456 μsec (multiply instruction)

Predecessor(s): IBM 604
Successor(s): IBM 704
Price: US$15,000/month (rental only)


The IBM 701 (initially known as the IBM Defense Calculator) was IBM's first commercial computer; it was later described as being "key to IBM's transition from punched-card machines to electronic computers". It was a vacuum tube scientific mainframe (built at a time when computers were generally only used for scientific, and not business, computing).

It was announced in April, 1952. 19 were produced (18 by June, 1954, when production ended; the last was a later special order for use in weather forecasting by the US government).

It was a fairly modern machine in architectual terms, compared to its close contemporary, the IBM 650; it was parallel, not serial, and it used binary internally. It used Williams tube electrostatic cathode ray tubes for main memory; each tube held 1K bits, and a bank contained 36 tubes. Configurations could have either one or two banks.

Secondary storage included up to 4 drums, each holding 2048 long-words, capable of transferring 800 words/second. A system included four magnetic tape drives, using 1/2" plastic tape; the first magnetic tape on a computer.

Other peripherals included a printer, and punched card reader and punch.

Further reading

  • Charles J. Bashe, Lyle R. Johnson, John H. Palmer, Emerson W. Pugh, IBM's Early Computers, MIT Press, Cambridge, 1986

External links