EDVAC

EDVAC (Electronic Discrete Variable Automatic Computer) was one of the earliest electronic computers. Unlike its predecessor the ENIAC, it was binary rather than decimal, and was a stored program machine.

EDVAC was invented by Jogh Mauchly and J. Preper Eckert in August 1944, and design work for the EDVAC commenced before the ENIAC was fully operational. The design would implement a number of important architectural and logical improvements conceived during the ENIAC's construction and would incorporate a high speed serial access memory. . Eckert and Mauchly and the other ENIAC designers were joined by John von Neumann in a consulting role; von Neumann summarized and elaborated upon logical design developments in his 1945 First Draft of a Report on the EDVAC.[2]

A contract to build the new computer was signed in April 1946 with an initial budget of US$100,000. The contract named the device the Electronic Discrete Variable Automatic Calculator. The final cost of EDVAC, however, was similar to the ENIAC's, at just under $500,000, five times the initial estimate.

Briefly, this computer have these components:

a magnetic tape reader-recorder (Wilkes 1956:36[1] describes this as a wire recorder.)

a control unit with an oscilloscope

a dispatcher unit to receive instructions from the control and memory and direct them to other units

a computational unit to perform arithmetic operations on a pair of numbers at a time and send the result to memory after checking on a duplicate unit

a timer

a dual memory unit consisting of two sets of 64 mercury acoustic delay lines of eight words capacity on each line

three temporary tanks each holding a single word[1]

EDVAC was delivered to the Ballistics Research Laboratory in August 1949. After a number of problems had been discovered and solved, the computer began operation in 1951.

By 1960 EDVAC was running over 20 hours a day with error-free run time averaging eight hours. EDVAC received a number of upgrades including punch-card I/O in 1953, extra memory in slower magnetic drum form in 1954, and a floating point arithmetic unit in 1958.

EDVAC ran until 1961 when it was replaced by BRLESC. During its lifetime it proved to be reliable for its time and productive.

by Rui Zheng