CDC 6600

The CDC 6600 was a mainframe computer from Control Data Corporation, first (first in the United States) delivered in 1964 to the Lawrence Radiation Laboratory, part of the University of California at Berkeley. It was used primarily for high energy nuclear physics research, particularly for the analysis of nuclear events photographed inside the Alvarez bubble chamber. The very first CDC 6600 was delivered about one year earlier to Conseil Européen pour la Recherche Nucléaire (CERN) near Geneva, Switzerland also for use in high energy nuclear physics research. It is generally considered to be the first successful supercomputer, outperforming its fastest predecessor, IBM 7030 Stretch, by about three times. With performance of about 1 megaFLOPS, it remained the world's fastest computer from 1964–69, when it relinquished that status to its successor, the CDC 7600.

The system organization of the CDC 6600 was used for the simpler (and slower) CDC 6400, and later a version containing two 6400 processors known as the CDC 6500. These machines were instruction-compatible with the 6600, but ran slower due to a much simpler and more sequential processor design. The entire family is now referred to as the CDC 6000 series. The CDC 7600 was originally to be compatible as well, starting its life as the CDC 6800, but during the design compatibility was dropped in favor of outright performance. While the 7600 CPU remained compatible with the 6600, allowing portable user code, the peripheral processor units (PPUs) were different, requiring a different operating system.

A CDC 6600 is on display at the Computer History Museum in Mountain View, California.