Editing Scientific Data Systems (section)

==History==
===Early machines===
Throughout the majority of the 1960s the US computer market was dominated by "Snow White", [[IBM]], and the "Seven Dwarves", [[Burroughs Corporation|Burroughs]], 
[[UNIVAC]], [[NCR Corporation|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 [[transistor]]s 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,<ref>{{cite book |last1=Gregory |first1=Nathan |title=The Tym Before ... |date=Mar 16, 2018 |publisher=Lulu |isbn=978-1-387-30405-9 |page=85 |url=https://books.google.com/books?id=UIFcDwAAQBAJ&pg=PA85 |access-date=Feb 15, 2020 |archive-date=December 17, 2022 |archive-url=https://web.archive.org/web/20221217093134/https://books.google.com/books?id=UIFcDwAAQBAJ&pg=PA85 |url-status=live }}</ref> rather than [[germanium]], which offered much better reliability for no real additional cost.<ref>{{cite web |last1=Scientific Data Systems |title=SDS 900 series |url=https://www.yumpu.com/en/document/view/42710052/sds-900-series-1965-ca |website=yumpu.com |access-date=Feb 15, 2020 |archive-date=February 15, 2020 |archive-url=https://web.archive.org/web/20200215171935/https://www.yumpu.com/en/document/view/42710052/sds-900-series-1965-ca |url-status=live }}</ref>

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),<ref>A programmed operator was a hardware concept on the SDS 900 series of computers similar to the concept of the [[Atlas Computer (Manchester)|Atlas computer]]'s "extracodes". The programmed operator calling mechanism allowed computer operation codes to be interpreted by software code. See Scientific Data Systems, [http://archive.computerhistory.org/resources/text/SDS/SDS.900.1962.102646286.pdf "SDS 900 Series"] {{Webarchive|url=https://web.archive.org/web/20081218041721/http://archive.computerhistory.org/resources/text/SDS/SDS.900.1962.102646286.pdf |date=2008-12-18 }}, technical manual. Cf. Programmed Operator. Also see [http://bitsavers.org/pdf/sds/9xx/910/900008D_910_RefMan_Feb70.pdf "SDS 910 Reference Manual"] {{Webarchive|url=https://web.archive.org/web/20110117070553/http://www.bitsavers.org/pdf/sds/9xx/910/900008D_910_RefMan_Feb70.pdf |date=2011-01-17 }}, February 1970. Cf. Appendix E. page A-19, "Programmed Operators" for an in-depth discussion of Programmed Operators.</ref><ref>Bell, Gordon, [http://research.microsoft.com/en-us/um/people/gbell/Computer_Structures__Readings_and_Examples/00000295.htm "Computer Structures: Readings and Examples"] {{Webarchive|url=https://web.archive.org/web/20081226125041/http://research.microsoft.com/en-us/um/people/gbell/Computer_Structures__Readings_and_Examples/00000295.htm |date=2008-12-26 }}, Section 6: Processors with multiprogramming ability, p.275. "The [SDS] 940 uses a memory map which is almost a subset of that of Atlas but is more modest than that of the IBM 360/67 [Arden et al., 1966] and GE 645 [Dennis, 1965; Daley and Dennis, 1968]. A number of instructions are apparently built in via the programmed operator calling mechanism, based on Atlas extracodes (Chap. 23). The software-defined instructions emphasize the need for hardware features. For example, floating-point arithmetic is needed when several computer-bound programs are run. The SDS 945 is a successor to the 940, with slightly increased capability but at a lower cost."</ref> 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 unit|floating point processor]] for higher performance. The performance increase was dramatic; the 910/920 needed 16 [[microsecond]]s to add two 24-bit [[integer]]s, the 9300 only 1.75, almost 10 times as fast. The 9300 also increased maximum memory from 16 [[kiloword|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 ({{Inflation|US|105000|1963|fmt=eq|r=-3}}). 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 [[input/output|I/O]] and the same compute power, but it is unclear whether this shipped.<ref name=Calkins>{{cite web |url=http://www.andrews.edu/~calkins/profess/SDSigma7.htm |title=The Computer That Will Not Die: The SDS SIGMA 7 |author=Keith G. Calkins |date=June 1984 |access-date=15 May 2011 |archive-date=25 May 2011 |archive-url=https://web.archive.org/web/20110525174115/http://www.andrews.edu/~calkins/profess/SDSigma7.htm |url-status=live }}</ref>

===SDS 92===
The '''SDS 92'''<ref name="SDS92Ref">{{Cite web
|url=http://www.bitsavers.org/pdf/sds/92/900505C_SDS_92_Reference_Jun65.pdf
|title=SDS 92 Reference Manual
|website=www.bitsavers.org
|access-date=March 16, 2019
|archive-date=March 27, 2020
|archive-url=https://web.archive.org/web/20200327193614/http://bitsavers.org/pdf/sds/92/900505C_SDS_92_Reference_Jun65.pdf
|url-status=live
}}</ref> is generally accepted as the first commercial computer using monolithic integrated circuits.<ref>{{Cite book|url=https://books.google.com/books?id=jfyvXAOhWXAC&q=%22SDS+92%22+delivered|title=The U.S. computer industry: a study of market power|last=Brock|first=Gerald W.|date=1975|publisher=Ballinger Pub. Co.|isbn=9780884102618|pages=192|language=en|quote=That same month [April 1965] Scientific Data Systems delivered the first commercial integrated circuit computer, the SDS-92.|access-date=2020-12-04|archive-date=2022-12-17|archive-url=https://web.archive.org/web/20221217093202/https://books.google.com/books?id=jfyvXAOhWXAC&q=%22SDS+92%22+delivered|url-status=live}}</ref><ref>{{cite book |last1=Pugh |first1=Emerson W. |last2=Johnson |first2=Lyle R. |last3=Palmer |first3=John H. |title=IBM's 360 and Early 370 Systems |date=1991 |publisher=MIT Press |isbn=9780262161237 |page=440 |url=https://books.google.com/books?id=MFGj_PT_clIC&q=%22sds+92%22&pg=PA440 |language=en |access-date=2020-12-04 |archive-date=2023-08-13 |archive-url=https://web.archive.org/web/20230813085115/https://books.google.com/books?id=MFGj_PT_clIC&q=%22sds+92%22&pg=PA440 |url-status=live }}</ref> ICs were used on about 50 circuit cards.<ref name=Calkins />

The SDS 92 is a small, high-speed, very low-cost, general purpose computer 12-bit system introduced in 1965.<ref name="SDS92Ref" /><ref>{{Cite book|url=https://books.google.com/books?id=cY0TAAAAIAAJ&q=%22sds+92%22|title=The Industrial Reorganization Act|date=1974|others=Columns: computer, solid state?, avg monthly rentals, date of 1st installation, number of installations, number of unfilled orders|pages=5577|language=en|access-date=2020-12-04|archive-date=2023-08-13|archive-url=https://web.archive.org/web/20230813085111/https://books.google.com/books?id=cY0TAAAAIAAJ&q=%22sds+92%22|url-status=live}}</ref> it was not compatible with other SDS lines such as the 900 series or the [[SDS Sigma series|Sigma series]].<ref>{{cite book|last1=Scientific Data Systems|title=Reference Manual SDS 92 Computer|date=June 1965|url=http://bitsavers.trailing-edge.com/pdf/sds/92/900505C_SDS_92_Reference_Jun65.pdf|access-date=Sep 20, 2014|archive-date=September 24, 2014|archive-url=https://web.archive.org/web/20140924053626/http://bitsavers.trailing-edge.com/pdf/sds/92/900505C_SDS_92_Reference_Jun65.pdf|url-status=live}}</ref> Features included:<ref name="SDS92Ref" />
*12- and 24-bit instructions
*12-bit word plus parity bit
*2048-word basic memory (1.75 [[microsecond|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:<ref name="SDS92Ref" />
*10 [[characters per second|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
*[[SDS 9 Series#MAGPAK|MAGPAK]] Magnetic Tape System

===Sigma series===
[[File:LCM - Xerox Sigma 9 (right) and related equipment - 01.jpg|thumb|An XDS Sigma 9 at the [[Living Computer Museum]], Seattle, Washington, 2014]]
In December 1966 SDS shipped the entirely new [[SDS Sigma series|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 [[processor register|registers]] rather than an [[Accumulator (computing)|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 [[Groupe Bull|CII]], as a licensee of SDS, sold about 60 Sigma 7 machines in Europe, and developed an upgrade with [[virtual memory]] and [[Multiprocessing|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.<ref>{{cite web |title=Graduate Studies Catalog |url=https://www.uwgb.edu/UWGBCMS/media/Catalog/files/1984-1986_GRAD.pdf |website=UW-Green bay |access-date=July 9, 2020 |archive-date=July 11, 2020 |archive-url=https://web.archive.org/web/20200711121245/https://www.uwgb.edu/UWGBCMS/media/Catalog/files/1984-1986_GRAD.pdf |url-status=live }}</ref><ref>{{cite web |last1=Spin |first1=William A. |title=ANNUAL HISTORICAL REVIEW KWAJALEIN MISSILE RANGE |url=https://nautilus.org/wp-content/uploads/2012/09/413-William-A.-Spin.pdf |website=Nautilus Institute |access-date=July 9, 2020 |archive-date=July 9, 2020 |archive-url=https://web.archive.org/web/20200709213228/https://nautilus.org/wp-content/uploads/2012/09/413-William-A.-Spin.pdf |url-status=live }}</ref> 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.<ref>{{cite book |last1=McMurran |first1=Marshall William |title=Achieving Accuracy: A Legacy of Computers and Missiles |date=2008 |publisher=Xlibris Corporation |isbn=978-1-4363-8107-9 |page=104 |url=https://books.google.com/books?id=UU3v0tbq8acC&pg=PA393 |access-date=Jul 9, 2020 |archive-date=August 7, 2020 |archive-url=https://web.archive.org/web/20200807043943/https://books.google.com/books?id=UU3v0tbq8acC&pg=PA393 |url-status=live }}</ref>