SDS Sigma Series

The SDS Sigma series was a series of computers that was introduced by Scientific Data Systems in 1966. The first machines in the series were the 16-bit Sigma 2 and the 32-bit Sigma 7; the Sigma 7 was the first 32-bit computer released by SDS. At the time the only competition for the Sigma 7 was the IBM 360.

Memory size increments for all SDS/XDS/Xerox computers was stated in kWords, not kBytes. For example, the Sigma 5 base memory was 16K 32-Bit words (64K Bytes). Maximum memory was limited by the length of the instruction address field of 17 bits, or 128K Words (512K Bytes). Although this is a trivial amount of memory in today's technology, Sigma systems performed their tasks exceptionally well, and few were deployed with, or needed, the maximum 128K Word memory size.

The Sigma series was commercially retired in the 1970s when Xerox, which bought SDS in 1969, left the mainframe computer business.

Read more about SDS Sigma Series:  Instruction Format, Clones

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