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Manufacturer: Remington Rand
Year Design Started: Early 1947
Year First Shipped: March, 1951
Form Factor: mainframe
Word Size: 72 bits
Logic Type: vacuum tubes
Design Type: serial asynchronous
Clock Speed: 2.25 Mhz
Instruction Speed: 120 μsec (add, excluding memory access)
Memory Speed: 400 μsec (maximum)
Physical Address Size: 3 digits (decimal)
Predecessor(s): EDVAC
Successor(s): UNIVAC II
Price: US$1250-1500K (system)

The UNIVAC I ('UNIVersal Automatic Computer'; originally, just plain UNIVAC, until later models appeared) was the first commercially-available computer in the US.

It was a vacuum tube machine, using mercury delay lines for main memory, with 1000 words organized as 100 lines of 10 words each (to reduce access times over fewer, larger lines). The CPU operated in digit-serial mode (i.e. a digit at a time), to match the memory. Its word size was 72 bits, with two instructions per word, with 12 digits/characters per word; it stored numbers with a form of packed decimal, with digits being represented as their character equivalents.

The only input/output devices were magnetic tape units, the 'UNISERVO'. Data could be transferred to and from tape with off-line peripherals which allowed use of printing, keyboard input, and punched cards.

A careful, slow power-on procedure, in which the filaments in the tubes were slowly warmed up, produced very reliable operation. (No doubt prior experience with tubes in the ENIAC had educated the UNIVAC's builders.)

Further reading

  • Nancy B. Stern, From ENIAC to UNIVAC: An Appraisal of the Eckert-Mauchly Computers, Digital Press, Bedford, 1981
  • Arthur Lawrence Norberg; Computers and Commerce: A Study of Technology and Management at Eckert-Mauchly Computer Company, Engineering Research Associates, and Remington Rand; MIT Press, Cambridge, 2005

External links