EDVAC

The EDVAC as installed in Building 328 at the Ballistics Research Laboratory.

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.

Project origin and plan

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.^[1] 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's Moore School of Electrical Engineering. 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.

Technical description

The EDVAC was a binary serial computer with automatic addition, subtraction, multiplication, programmed division and automatic checking with an ultrasonic serial memory^[1] 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:

• 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'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.

Installation and operation

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 and the University of Pennsylvania, resulting in Eckert and Mauchly's resignation and departure 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 operational life it proved to be reliable and productive for its time.

References

1. ^ ^{a b c d} Wilkes, M. V. (1956). Automatic Digital Computers. New York: John Wiley & Sons. pp. 305 pages. QA76.W5 1956. 
2. ^ "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. .

External Links

• Oral history interview with J. Presper Eckert, Charles Babbage Institute, University of Minnesota. Eckert, a co-inventor of the ENIAC, discusses its development at the University of Pennsylvania. He describes the difficulty in securing patent rights for the ENIAC and the problems posed by the circulation of John von Neumann's 1945 First Draft of the Report on EDVAC, which placed the ENIAC inventions in the public domain. Eckert deaccentuates von Neumann's role in the development of EDVAC.
• Oral history interview with Carl Chambers, Charles Babbage Institute, University of Minnesota. Chambers discusses John von Neumann's involvement from 1944 in the EDVAC project, the financial strains that accompanied this project, and the patent disagreement that led Eckert and Mauchly to resign from the faculty. He concludes with his views on the importance of the 1946 Moore School summer course.
• Oral history interview with Irven A. Travis, Charles Babbage Institute, University of Minnesota. Travis describes the ENIAC project at the University of Pennsylvania (1941-46), the technical and leadership abilities of chief engineer J. Presper Eckert, the working relations between Mauchly and Eckert, the disputes over patent rights, and their resignation from the university. Oral history interview by Nancy B. Stern, 21 October 1977.
• Oral history interview with S. Reid Warren, Charles Babbage Institute, University of Minnesota. Warren served as supervisor of the EDVAC project; central to his discussion are J. Presper Eckert and John Mauchly and their disagreements with administrators over patent rights; discusses John von Neumann's 1945 draft report on the EDVAC, and its lack of proper acknowledgment of all the EDVAC contributors.
• Oral history interview with Frances E. Holberton, Charles Babbage Institute, University of Minnesota. Holberton describes her work at Eckert-Mauchly Computer Corporation, David Taylor Model Basin, and the National Bureau of Standards, and the difficulties she encountered as a woman. She recounts her work on ENIAC and LARC, her design of operating systems, and her applications programming. Interview by James Baker Ross, 14 April 1983. Charles Babbage Institute