A vacuum tube computer is a computer system built primarily using vacuum tubes and vacuum tube logic. Vacuum tube switching replaced the earlier relay computers from the 1940s. Vacuum tube computer gained traction during the 1950s through the early 1960s. By the mid 1960s discrete logic computers superseded vacuum tubes.

Overview

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Early relay computers were rather slow - operating at just 1Hz ((or one switching operation each second). They were cheap and readily available due to their widespread use in telephone systems. Vacuum tubes prove to be a significant improvement over electromechanical relays - operating 1000 times faster. However the performance advantage came at the cost of decreased reliability and maintainance. Tube failure was frequent, running hot and burning out rapidly.

Vacuum Tube Systems

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System	Developer	Company/Institution	Tube Count	Year	Notes
ABC	John Vincent Atanasoff	Iowa State University	300	1940
Colossus Mark 1		Post Office Research Station	1,600	1943
Colossus Mark 2		Post Office Research Station	2,400	1944
ENIAC		University of Pennsylvania	17,468	1946	relays/vacuum tubes hybrid
SSEM		Victoria University of Manchester		1948
BINAC		EMCC	700	1949
EDSAC	Maurice Wilkes	University of Cambridge	3,000	1949
Manchester Mark I		Victoria University of Manchester	1,300	1949
CSIRAC	Trevor Pearcey		2,000	1949
MADDIDA		Northrop Aircraft	53	1949
SEAC		NIST	747	1950
Pilot ACE		National Physical Laboratory	800	1950
SWAC		NIST	2,300	1950
UNIVAC 1101		ERA	2,700	1950
Ferranti Mark I		Ferranti	4,050	1951
UNIVAC I		EMCC	5,200	1951
Whirlwind I		MIT	12,500	1951
Whirlwind II		MIT	50,000	1951	Never completed, AN/FSQ-7 a direct derivative
EDVAC		University of Pennsylvania	6,000	1951
WITCH		Harwell	828	1951	Made with 480 relays, 828 Dekatron valves for math
ORDVAC		University of Illinois	2,178	1951
LEO I			5,936	1951
IAS Computer		IAS		1952

See also

• relay computer

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