Throughout the majority of the 1960s the US computer market was dominated by "Snow White", IBM, and the "Seven Dwarves", Burroughs, UNIVAC, NCR, Control Data Corporation, Honeywell, General Electric, and RCA.

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.

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.

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.

[11][12] 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.

Jack Mitchell, William L. Scheding, and Henry Harold, along with some other former SDS engineers introduced a microprocessor-based computer called the SDS-420[14] built on a 6502A-based processor design with up to 56 KB of memory and a proprietary OS, SDS-DOS, along with the BASIC programming language from Microsoft.

The SDS-420 featured a dual single-sided-double-density (400 KB per side) floppy disk drive, Model 70, manufactured by PerSci (Peripheral Sciences), of Santa Monica and Marina del Rey, California.

Other hardware options were a 6551-A USART and a proprietary network SDS-NET using a Z8530 SDLC/HDLC chip and software patterned after the early Xerox 3.0 Mbit/s Ethernet and transceivers produced by Tat Lam of the Bay Area.

SDS announced a fully operational local area network (LAN)-based file server called SDS-NET at COMDEX in the early 1980s.

The SDS 430 Server offered file and printer sharing services over SDS-NET or using a modem and was based upon a 10 MB hard disk manufactured by Micropolis of Chatsworth, California.

Through partnerships with their value-added resellers (VARs) other software product offerings included a solid-waste management system with automated truck routing and a country-club accounting package.

One UK-based VAR was Jacq-Rite, a vertical market software house run by Ken Groome and Vivienne Gurney and based in Dorking, Surrey.

Jacq-Rite had developed a range of specialist insurance software for the Jacquard machine but transferred to the SDS 400 following the advice of John McCully.

In an attempt to bypass these problems Hill produced a clone of the 4000 series computer by reverse-engineering an original model with the aid of a set of paper schematics obtained on a visit to SDS.

This was fortunate because, being unable to confer with SDS, Hill had unwittingly used schematics referring to a forthcoming revision of the machine, for which no firmware had yet been completed.

This was supplied with bespoke software (also produced by Hill, with the assistance of Paula Flint) to store examination results and print certificates.

Taking advantage of the SCSI implementation, Hill added an external connector to his version of the machine and developed a matching hard drive enclosure.

However, the UK company's lack of capital to invest in the machine's manufacture meant that the cosmetic appearance of the computer left a lot to be desired.

Furthermore, the machines were extremely costly – IBM's new Personal Computer/AT was shipping at about half the price SDS UK Limited needed to sell their computer for.

Developments and improvements by Comshare included the I-Channel, which allowed the utilization of Bus/Tag (IBM compatible) devices and the ISI Communications interface.

These innovations allowed Comshare to capitalize on the Sigma CPU's and their software development (Commander II) by gaining access to current technology storage systems.

When Xerox withdrew from the mainframe computer manufacturing business and relinquished all assets to Honeywell Corporation, Comshare opened a Research and Development facility in Phoenix Arizona, where they manufactured three Sigma 9 systems from spare and remanufactured parts acquired from Modutest, Inc. of Westlake Village, California and Modutest Systems, Inc., Phoenix, Arizona.

In March 1982 Honeywell gave the remaining software for the 900 series to a group in Kansas City that offered to continue making copies for people still using the systems.

In September 2006, this collection was donated to the Computer History Museum along with all of the program's original documentation, and copies of most of the SDS user's manuals.