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CDC 6600

The CDC 6600 was a mainframe computer from Control Data Corporation built in 1965. It is generally considered to be the first supercomputer and completely outperformed all other machines in the world by a wide margin, typically 10 to 1. It it generally agreed to have been the world's fastest computer from 1965 to 1969, when it was replaced by its own successor, the CDC 7600.

The CDC 6600 was designed by Seymour Cray as soon as work had completed on the CDC 3600, a much smaller computer. With sales of their other machines doing well, CDC allowed Cray as much time as he liked to build his next design.

The basis for the 6600 is what we would today refer to as a RISC system, one in which the processor is tuned to do instructions which are comparatively simple. The philosohy of many other machines was toward using instructions which were complicated - for example, which would fetch an operand from memory and add it to a value in a register. In the 6600, loading the value from memory would require one instruction, and adding it would require a second.

To handle the "day to day" tasks which other designs put in the CPU, Cray included in the 6600 10 copies of another kind of processor, based in many ways on his earlier computer, the 160A. These machines, called peripheral processors, or PPUs, were full computers in their own right, but tuned to performing I/O tasks, and running the operating system. When the main CPU needed to perform some sort of I/O, it instead sent (or loaded) a small program into one of these other machines.

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