SDS Sigma series
The SDS Sigma series from SDS was a family of 16-bit and 32-bit computers (see below). They were intended for use partially or wholly in real-time settings, but also provided batch processing facilities (also time-sharing, on the 32-bit systems). This dual capability was described as "multi-use" in SDS' marketing material.
The Sigma 6, 8 and 9 were all produced after the merger of SDS and Xerox (forming 'Xerox Data Systems', 'XDS') in March 1969. Xerox sold XDS to Honeywell in 1975; Honeywell briefly continued support of the Sigmas, but then terminated it. At that point, other companies, including Telefile, Ilene Industries Data Systems, and Realtime Computer Equipment started to build and sell program compatible machines.
A Sigma 7 at UCLA was the first computer connected to the nascent ARPANET.
Contents
Family members
There were two lines of program compatible machines; a 16-bit group and a 32-bit group. All use a load-store architecture.
Below are thumbnail descriptions of the models in the Sigma family, in the order of their dates of introduction.
16-bit group
Their instruction set includes 'memory reference' instructions:
| Opcode | R | I | X | S | Displacement | ||||||||||
| 15 | 14 | 13 | 12 | 11 | 10 | 09 | 08 | 07 | 06 | 05 | 04 | 03 | 02 | 01 | 00 |
- R - Self-relative
- I - Indirect
- X - Indexed
- S - Base-relative
There are also 'copy' instructions (register-to-register operations) and conditional branch instructions.
Sigma 2
First member of the of the Sigma 16-bit group; introduced in 1966.
Sigma 3
Introduced in 1966.
32-bit group
Their instruction set is also principally 'memory reference' instructions:
| I | Opcode | R | X | Address | |||||||||||||||||||||||||||||
| 00 | 01 | 02 | 03 | 04 | 05 | 07 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | ||
- R - Register (in current register block)
- X - Index register
Again, there are also 'copy' instructions (register-to-register operations) and conditional branch instructions.
Sigma 7
First member of the of the Sigma 32-bit group; announced in April, 1966.
Sigma 5
Introduced in 1967; a reduced-cost version, without separate input/output processors.
Sigma 6
Announced in May, 1970; SDS' initial entry into commercial business data processing.
Sigma 9
Announced in October 1970.
Sigma 8
Introduced in 1972.
External links
- sigma - documentation on Bitsavers
- The Sigma Family - sales brochure; pre-dates the Xerox merger
- Guide to the Keith G. Calkins collection on Sigma systems
- The SDS Sigma 7: A Real-Time Time-Sharing Computer
- The Computer That Will Not Die: The SDS Sigma 7 Narrator: it died.
- 3420 Boelter Hall: Where It All Began - UCLA Internet Museum, displaying a Sigma 7 front panel
