From Wikipedia, the free encyclopedia

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.

Contents 1 Project origin and plans 2 Technical description 3 Installation and operation 4 References

The design for the EDVAC was developed before the ENIAC was even operational. It was intended to resolve many of the problems created by the ENIAC's design. Like the ENIAC, the EDVAC was built for the U.S. Army's Ballistics Research Laboratory at the Aberdeen Proving Ground by the University of Pennsylvania. The ENIAC designers Eckert & Mauchly were joined by John von Neumann and some others and the new design was based on von Neumann's 1945 report, First Draft of a Report on the EDVAC.^[1]

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

The computer that was built was to be binary with automatic addition, subtraction, multiplication, programmed division and automatic checking with a 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 was built out of the following components:

• a magnetic tape reader-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

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 & Mauchly and the University of Pennsylvania. This resulted in Eckert and Mauchly leaving to form the Eckert-Mauchly Computer Corporation and taking most of the senior engineers with them.

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 had proved to be reliable for its time and productive.

1. ^ "First Draft of a Report on the EDVAC" (PDF format) by John von Neumann, Contract No.W-670-ORD-4926, between the United States Army Ordnance Department and the University of Pennsylvania. Moore School of Electrical Engineering, University of Pennsylvania, June 30, 1945. The report is also available in Stern, Nancy (1981). From ENIAC to UNIVAC: An Appraisal of the Eckert-Mauchly Computers. Digital Press. .