CDC-6600

CDC 6x00 registers

⁵₉	. . .	¹₇	. . .	⁰₀	(bit position)
Operand registers (60 bits)
X0					Register 0
X1					Register 1
X2					Register 2
X3					Register 3
X4					Register 4
X5					Register 5
X6					Register 6
X7					Register 7
Address registers (18 bits)
		A0			Address 0
		A1			Address 1
		A2			Address 2
		A3			Address 3
		A4			Address 4
		A5			Address 5
		A6			Address 6
		A7			Address 7
Increment registers (18 bits)
		B0 (all bits zero)			Increment 0
		B1			Increment 1
		B2			Increment 2
		B3			Increment 3
		B4			Increment 4
		B5			Increment 5
		B6			Increment 6
		B7			Increment 7

The CDC 6600 was the flagship mainframe supercomputer of the 6000 series of computer systems manufactured by Control Data Corporation. It was notable in several respects; exceptionally fast for its day, it anticipated the RISC design philosophy and (unusually) employed ones'-complement representation of integers. Its successors would continue the architectural tradition for more than 30 years until the late 1980s, and were the last ones'-complement original designs, being outlasted only by the UNIVAC 1100/2200 series.

The first CDC 6600 was delivered in 1965 to the CERN laboratory near Geneva, Switzerland, where it was used to analyse the two to three million photographs of bubble-chamber tracks that CERN experiments were producing every year. In 1966 another CDC 6600 was delivered to the Lawrence Radiation Laboratory, part of the University of California at Berkeley, where it was used for the analysis of nuclear events photographed inside the Alvarez bubble chamber. The University of Texas at Austin had one delivered for its Computer Science and Mathematics Departments, and installed underground on its main campus, tucked into a hillside with one side exposed, for cooling efficiency. The CDC 6600 is generally considered to be the first successful supercomputer, outperforming its fastest predecessor, the IBM 7030 Stretch, roughly by a factor of three. With performance of up to three megaFLOPS, the CDC 6600 was the world's fastest computer from 1964 to 1969, when it relinquished that status to its successor, the CDC 7600.

A CDC 6600 is on display at the Computer History Museum in Mountain View, California. The only running CDC 6000 series machine has been restored by Living Computers: Museum + Labs.

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