CDC 6600

The CDC 6600 was a mainframe computer from Control Data Corporation built in 1965. It is generally considered to be the first successful supercomputer and completely outperformed all other machines in the world by a wide margin, typically 10 to 1. It is 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, Control Data 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 philosophy 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 'household' tasks which other designs put in the CPU, Cray included in the 6600 ten other processors, based partly on his earlier computer, the CDC 160A. These machines, called peripheral processors, or PPs, 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 loaded a small program into one of these other machines. The central processor had 60-bit words, while the peripheral processors had 12-bit words (like the later DEC PDP-8 minicomputer).\nCDC used the term byte to refer to 12-bit quantities used by peripheral processors; characters were 6-bit, and central processor instructions were either 15 bits, or 30 bits with an 18-bit address field, the latter allowing for a directly addressable memory space of 256 K words (converted to modern terms, with 8-bit bytes, this is the same amount of bits as in a memory of 1.88 megabytes).

See also

\n*CDC 6600 CP architecture\n*CDC 6600 PP architecture

External links

\n*Presentation of the CDC 6600 and other machines designed by Seymour Cray – by C. Gordon Bell of Microsoft Research (formerly of DEC)