The story
Founded by Max Palevsky on Sep 1961.1
Early machines
Throughout the majority of the 1960s the US computer market was dominated by "Snow White" (IBM), and the "Seven Dwarfs", Burroughs, UNIVAC, NCR, Control Data Corporation, Honeywell, General Electric, and RCA. SDS entered this well-developed market and was able to introduce a time-sharing computer at just the right time. Much of their success was due to the use of silicon-based transistors in their earliest designs, the 24-bit SDS 910 and SDS 920 which included a hardware (integer) multiplier. These are arguably the first commercial systems based on silicon, rather than germanium, which offered much better reliability for no real additional cost.
Additionally, the SDS machines shipped with a selection of software, notably a FORTRAN compiler, developed by Digitek, that made use of the systems' Programmed OPeratorS (POPS), and could compile, in 4K 24-bit words, programs in a single pass without the need for magnetic tape secondary storage. For scientific users writing small programs, this was a real boon and dramatically improved development turnaround time.
The 910 and 920 were joined by the SDS 9300, announced in June 1963. Among other changes, the 9300 included a floating-point processor for higher performance. The performance increase was dramatic; the 910/920 needed 16 microseconds to add two 24-bit integers, the 9300 only 1.75, almost 10 times as fast. The 9300 also increased maximum memory from 16 kWords to 32 kWords. Although its instruction format resembled that of the earlier machines, it was not compatible with them.
In December 1963 SDS announced the SDS 930, a major re-build of the 9xx line using integrated circuits (ICs) in the central processor. It was comparable to the 9300 in basic operations, but was generally slower overall due to the lack of the 9300's memory interlace capability and hardware floating-point unit (although a hardware floating-point "correlation and filtering unit" was available as an expensive option). The 930 cost less than half that of the original 9300, at about $105,000 (equivalent to $1,104,000 in 2025). Cut-down versions of the 920 also followed, including the 12-bit SDS 92, and the IC-based 925.
Project Genie developed a segmentation and relocation system for time-sharing use on the 930 at the University of California, Berkeley, which was commercialized in the SDS 940. It had additional hardware for relocation and swapping of memory sections, and interruptible instructions. The 940 would go on to be a major part of Tymshare's circuit-switched network system growth in the 1960s (pre-ARPAnet and before packet-switching). A 945 was announced in July 1968 as a modified 940 with less I/O and the same computation power, but it is unclear whether this shipped.
SDS 92
The SDS 92 is generally accepted as the first commercial computer using monolithic integrated circuits. ICs were used on about 50 circuit cards.
The SDS 92 is a small, high-speed, very low-cost, general-purpose computer 12-bit system introduced in 1965. it was not compatible with other SDS lines such as the 900 series or the Sigma series. Features included:
12- and 24-bit instructions
Read the full text
12-bit word plus parity bit
2048-word basic memory (1.75 μsec memory cycle) expandable to 4096, 8192, 16,384 or 32,768 words, all directly addressable
Peripheral equipment available from SDS standard peripheral line included:
10 cps (characters per second) Keyboard/printer (teletype) with or without paper tape reader and punch
300 cps paper tape reader
60 cps paper tape punch
MAGPAK Magnetic Tape System
Sigma series
In December 1966 SDS shipped the entirely new Sigma series, starting with the 16-bit Sigma 2 and the 32-bit Sigma 7, both using common hardware internally. The success of the IBM System/360 and the rise of the 7-bit ASCII character standard was pushing all vendors to the 8-bit standard from their earlier 6-bit ones. SDS was one of the first companies to offer a machine intended as an alternative to the IBM System/360; although not compatible with the 360, it used similar data formats, the EBCDIC character code, and in other ways, such as its use of multiple registers rather than an accumulator, it was designed to have specifications that were comparable to those of the 360.
Various versions of the Sigma 7 followed, including the cut-down Sigma 5 and re-designed Sigma 6. The Xerox Sigma 9 was a major re-design with instruction lookahead and other advanced features, while the Sigma 8 and Sigma 9 mod 3 were low-end machines offered as a migration path for the Sigma 5. The French company CII, as a licensee of SDS, sold about 60 Sigma 7 machines in Europe, and developed an upgrade with virtual memory and dual-processor capability, the Iris 80. CII also manufactured and sold some 160 Sigma 2 systems.
The Sigma range was very successful in the niche real-time processing field, due to the sophisticated hardware interrupt structure and independent I/O processor. The first node of ARPANET was established by Leonard Kleinrock at UCLA with an SDS Sigma 7 system.
Xerox models
Even with these successes, when Xerox bought the company in 1969 they sold only about 1% of the computers in the United States, something Xerox never seemed to improve. When they were purchased, about 1,000 SDS machines of all types were in the market, and by the time the division closed in 1975 this had increased to only about 2,100. By this point, the newer Xerox 550 and 560 models, extensively re-designed Sigmas, were about to come to market and were extensively back-ordered. Most rights were sold to Honeywell in July 1975 who produced Sigmas for a short period, and provided support into the 1980s.
Several manufacturers attempted to enter the Sigma 9 replacement market. The first successful design was the Telefile T-85, but it is not clear how many were sold. Other efforts, including the Modutest Mod 9, Ilene Model 9000 and Real-time RCE-9 were designed, but it is not clear if they were ever produced past the prototype stage.
From Wikipedia’s article on Scientific Data Systems, shared under CC BY-SA 4.0.4