The UNIVAC I (UNIVersal Automatic Computer I) was the first general-purpose electronic digital computer design for business application produced in the United States. It was designed principally by J. Presper Eckert and John Mauchly, the inventors of the ENIAC. Design work was started by their company, Eckert–Mauchly Computer Corporation (EMCC), and was completed after the company had been acquired by Remington Rand (which later became part of Sperry, now Unisys). In the years before successor models of the UNIVAC I appeared, the machine was simply known as “the UNIVAC”.
The first Univac was accepted by the United States Census Bureau on March 31, 1951, and was dedicated on June 14 that year. The fifth machine (built for the U.S. Atomic Energy Commission) was used by CBS to predict the result of the 1952 presidential election. With a sample of a mere 5.5% of the voter turnout, it famously predicted an Eisenhower landslide.
The first contracts were with government agencies such as the Census Bureau, the U.S. Air Force, and the U.S. Army Map Service. Contracts were also signed by the ACNielsen Company, and the Prudential Insurance Company. Following the sale of Eckert–Mauchly Computer Corporation to Remington Rand, due to the cost overruns on the project, Remington Rand convinced Nielsen and Prudential to cancel their contracts.
The first sale, to the Census Bureau, was marked with a formal ceremony on March 31, 1951, at the Eckert–Mauchly Division’s factory at 3747 Ridge Avenue, Philadelphia. The machine was not actually shipped until the following December, because, as the sole fully set-up model, it was needed for demonstration purposes, and the company was apprehensive about the difficulties of dismantling, transporting, and reassembling the delicate machine. As a result, the first installation was with the second computer, delivered to the Pentagon in June 1952.
Originally priced at US$159,000, the UNIVAC I rose in price until they were between $1,250,000 and $1,500,000. A total of 46 systems were eventually built and delivered.
The UNIVAC I was too expensive for most universities, and Sperry Rand, unlike companies such as IBM, was not strong enough financially to afford to give many away. However, Sperry Rand donated UNIVAC I systems to Harvard University (1956), the University of Pennsylvania (1957), and Case Institute of Technology in Cleveland, Ohio (1957). The UNIVAC I at Case was still operable in 1965 but had been supplanted by a UNIVAC 1107.
A few UNIVAC I systems stayed in service long after they were made obsolete by advancing technology. The Census Bureau used its two systems until 1963, amounting to 12 and 9 years of service, respectively. Sperry Rand itself used two systems in Buffalo, New York until 1968. The insurance company Life and Casualty of Tennessee used its system until 1970, totaling over 13 years of service.
UNIVAC I used about 5,000 vacuum tubes, weighed 16,686 pounds (8.3 short tons; 7.6 t), consumed 125 kW, and could perform about 1,905 operations per second running on a 2.25 MHz clock. The Central Complex alone (i.e. the processor and memory unit) was 4.3 m by 2.4 m by 2.6 m high. The complete system occupied more than 35.5 m² (382 ft²) of floor space.
Eckert and Mauchly were uncertain about the reliability of digital logic circuits and little was known about them at the time. The UNIVAC I was designed with parallel computation circuits and result comparison. In practice, only failing components yielded comparison faults as their circuit designs were very reliable. Tricks were used to manage the reliability of tubes. Prior to use in the machine, large lots of the predominant tube type 25L6 were burned in and carefully tested. Often half of a production lot would be thrown away. Technicians installed a tested and burned-in tube in an easily diagnosed location such as the memory recirculate amplifiers. Then, when aged further, this “golden” tube was sent to stock to be used in a difficult to diagnose logic position. It took about 30 minutes to turn on the computer as all filament power supplies were stepped up to operating value over that time, to reduce in-rush current and thermal stress on the tubes. As a result, uptimes (MTBF) of many days to weeks were obtained on the processor. The UNISERVO did not have vacuum columns but springs and strings to buffer tape from the reels to the capstan. These were a frequent source of failures.
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