On April 29, 1952 IBM President Thomas J. Watson, Jr., informed his company's stockholders at the annual meeting that IBM was building "the most advanced, most flexible high-speed computer in the world." Known as the Defense Calculator while in development, the new machine emerged from the IBM Poughkeepsie Laboratory later that year and was formally unveiled to the public on April 7, 1953 as the IBM 701 Electronic Data Processing Machines.
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The IBM 701 and was IBM’s first commercial scientific computer. Its business computer siblings were the IBM 702 and IBM 650. The system used electrostatic storage, consisting of 72 Williams tubes with a capacity of 1024 bits each, giving a total memory of 2048 words of 36 bits each. Each of the 72 Williams tubes was three inches in diameter. Memory could be expanded to a maximum of 4096 words of 36 bits by the addition of a second set of 72 Williams tubes or by replacing the entire memory with magnetic core memory. The Williams tube memory and later core memory each had a memory cycle time of 12 microseconds. The Williams tube memory required periodic refreshing, mandating the insertion of refresh cycles into the 701s timing.
About 19 IBM 701 machines were built from 1952 to 1955. Most of these were sent to government agencies for defense, atomic research, aerodynamic and analysis of flight test data. |
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| IBM 701 console. The machine used about 150 Williams Tubes (2.5" CRTs) for their memory. Each tube stored a 32 x 32 bit array on its face. |
| With delivery of the IBM 701 in 1954 to Lawrence Livermore National Laboratory, the Laboratory dramatically improved its capability to perform scientific calculations. The machine was 12 times faster than its predecessor, the Univac-1, which the Laboratory acquired during its first year of operation. This would have reduced the time needed for nuclear explosives computations from the 100 hours they had been running to about eight hours. Instead, the 100-hour runs continued, although the programs gave improved results because of finer resolution and more detailed physics.
The successor of the 701 was the index register-equipped IBM 704, introduced 4 years after the 701. CRT memory storage was eventually superseded in new systems in about 1955 by a cheaper random access store called the "magnetic core store."
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| Williams, Crawley and McPherson admiring the implementation of the Williams Tube in an IBM 701 in 1953. |
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