CDC 7600

The CDC 7600 was the Seymour Cray-designed successor to the CDC 6600, extending Control Data's dominance of the supercomputer field into the 1970s. The 7600 ran at 36.4 MHz (27.5 ns clock cycle) and had a 65 Kword primary memory using magnetic core and variable-size (up to 512 Kword) secondary memory (depending on site). It was generally about ten times as fast as the CDC 6600, and could deliver about 10 MFLOPS on hand-compiled code, with a peak of 36 MFLOPS. In addition, in benchmark tests in early 1970 it was shown to be slightly faster than its IBM rival, the IBM System/360, Model 195. When the system was released in 1969, it sold for around $5 million in base configurations, and considerably more as options and features were added.

Design

After the 6600 started to near production quality, Cray lost interest in it and turned to designing its replacement. Making a machine "somewhat" faster would not be too difficult in the late 1960s; the introduction of integrated circuits allowed for denser packing of components, and in turn a higher clock speed. Transistors in general were also getting somewhat faster as the production processes and quality improved. However these sorts of improvements might be expected to make a machine twice as fast, perhaps as much as five times, but not the tenfold increase he demanded. Likewise the 6600 already had a hard time filling its existing ten functional units, so simply adding more parallelism wouldn't help all that much.