Alternate History

IBM 7030 (Caroline Era)

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The IBM 7030 "STRETCH" was an early transistorised computer designed by IBM and sold to Los Alamos in 1960. It was characterised by a number of features also found in the later IBM 360 mainframe, which was in turn highly influential.


IBM and UNIVAC were invited to bid for the contract to design a computer for the University of California Radiation Laboratory at Livermore. In order to meet the deadline and budget, they opted to use the older surface barrier transistor design rather than the newer diffusion type, which were also held not to have a sufficient track record to be reliable. The speed fell lamentably short of the expected hundred-fold increase in processing speed above the older IBM 704 and was in fact only three times faster because of the cost and technological constraints. This claim is typical of that time, when computers were expected to increase in performance exponentially, whereas this did not in fact come to pass. Nonetheless, IBM won the contract and delivered the computer, which was a success in business terms because it was "good enough".


As well as being successful, the IBM 7030 was influential on the design of future IBM mainframes. It was able to multitask, a facility which was used in many later computers and eventually enabled the Sinclair Ambassador to be built inexpensively and compactly due to it generating the display in software rather than with dedicated hardware. It also used a six-bit byte, a word-length also used in the 360, and generalised interrupts. However, a number of early features were suggested which had to be omitted due to expense and lack of space, including the decoding of future instructions simultaneously with the execution of the previous one and the loading of an instruction from memory before it was needed. These features also proved impractical because the circuitry required would not have operated fast enough to confer any advantage and the ideas were dropped.

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