Editing Scientific Data Systems (section)

===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>