ENIAC inventors John Mauchly and J.
Presper Eckert proposed the EDVAC's
construction 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.
Like the ENIAC, the EDVAC was built for the U.S. Army's Ballistics Research
Laboratory at the Aberdeen Proving Ground by the
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.
The EDVAC was a binary serial computer with automatic addition, subtraction, multiplication, programmed division and automatic checking with an ultrasonic serial memory capacity of 1,000 44-bit words (later set to 1,024 words, thus giving a memory, in modern terms, of 5.5 kilobytes).
Physically, the computer comprised the following components:
EDVAC's addition time was 864 microseconds and its multiplication time was 2900 microseconds (2.9 milliseconds).
The computer had almost 6,000 vacuum tubes and 12,000 diodes, and consumed 56 kW of power. It covered 490 ft² (45.5 m²) of floor space and weighed 17,300 lb (7,850 kg). The full complement of operating personnel was thirty people for each eight-hour shift.
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 although only on a limited basis. Its completion was delayed
because of a dispute over patent rights between Eckert and Mauchly
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 operational life it proved to be reliable and productive for its time.