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EDVAC

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The EDVAC, or Electronic Discrete Variable Automatic Computer, was a landmark in the history of computing.

Edvac
Edvac

It was one of the earliest electronic computers ever built. Developed at the Moore School of Electrical Engineering at the University of Pennsylvania, it served as a successor to the ENIAC. While the ENIAC used a decimal system, the EDVAC utilized a binary system. This means it operated using base-two logic rather than base-ten. This shift allowed the machine to function as a stored-program computer. This capability changed the way machines processed information forever.

The machine functioned as a binary serial computer. It could perform several arithmetic operations automatically, such as addition, subtraction, and multiplication. It also handled programmed division and included automatic checking features.

Screen Shot 2020-09-06 at 8.58.54 AM big
Screen Shot 2020-09-06 at 8.58.54 AM big

To store information, it used an ultrasonic serial memory. This system relied on 64 mercury acoustic delay lines to hold data. The memory had a capacity of 1,024 words, with each word consisting of 44 bits. In modern terms, this provided a memory capacity of approximately 5.6 kilobytes.

The physical components of the EDVAC were massive and complex. The computer contained 5,937 vacuum tubes and 12,000 diodes. It required 56 kilowatts of power to operate. The machine occupied 490 square feet of floor space. To keep the system running, a full complement of thirty people was needed for every eight-hour shift. The hardware also included a magnetic tape reader-recorder and a control unit equipped with an oscilloscope. A dispatcher unit sent instructions from the control and memory to other parts of the system.

Many significant figures contributed to the development of the EDVAC. John Mauchly and J. Presper Eckert, the inventors of the ENIAC, proposed the construction in August 1944. They were joined by John von Neumann, who served in a consulting role. Between February and June 1945, von Neumann wrote the "First Draft of a Report on the EDVAC." This document summarized the logical design developments of the machine. The project faced challenges when Eckert and Mauchly left the Moore School in March 1946. They did this because of a disagreement over a new university patent policy. They subsequently founded the Electronic Control Company in Philadelphia.

Financial details show how much the project grew during its development. An initial contract was signed in April 1946 with a budget of US$100,000. However, the final cost of the EDVAC reached just under $500,000. The machine was eventually delivered to the Ballistic Research Laboratory in 1949. It began limited operations in 1951 after engineers solved various technical problems. By 1952, the computer was running for several hours each day. By 1957, its usage increased to over 20 hours per day, with an average error-free runtime of 8 hours.

Speed and precision were central to the EDVAC's performance. The average time for an addition operation was 864 microseconds. This allowed for about 1,160 operations per second. Multiplication was slower, taking an average of 2,900 microseconds. This resulted in about 340 operations per second. The time required for an operation depended on the memory access time. This time varied based on the memory address and the current point in the serial memory's recirculation cycle. The machine could also perform floating-point arithmetic using specific bit allocations for the mantissa and the power of two.

The legacy of the EDVAC is found in the Von Neumann architecture. This term describes the stored-program concept where instructions are kept in the same memory as the data. John von Neumann's report proposed this major enhancement to the design. This architecture was later used by the EDSAC at Cambridge and the Manchester Baby. Most modern computers follow this design today. Computers that keep programs and data in separate memories are instead called the Harvard architecture. The EDVAC remained in service until 1962, when it was finally replaced by the BRLESC.

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