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IBM 7094

The IBM 7094 the fourth member of the most popular family of IBM's large second-generation transistorized mainframe computers and was designed for "large-scale scientific and technological applications". The first 7094 installation was in September 1962. In April 1964, the first 7094 II was installed, which had almost twice as much general speed as the earlier IBM 7090 due to a faster clock cycle and introduction of overlapped instruction execution.

NASA used 7094s to control the Mercury and Gemini space flights. Apparently, the US Air Force retired the last 7094s in service from the Ballistic Missile Early Warning System ("BMEWS") in the 1980s after almost 30 years of use.

Instruction Format

The basic instruction format was a 3-bit prefix, 15-bit decrement, 3-bit tag, and 15-bit address. The prefix field specified the class of instruction. The decrement field often contained an immediate operand to modify the results of the operation, or was used to further define the instruction type. The three bits of the tag specified seven index registers, the contents of which were subtracted from the address to produce an effective address. The address field either contained an address or an immediate operand.