View source for SDS 940

{{Short description|Machine designed to support time-sharing}}
{{Infobox information appliance
|image        = <!--[[File:SDS 940_computer.jpg|300px|Hardware]] http://www.computerhistory.org/collections/catalog/102669852-->
|type         = [[Mainframe computer]]
|release date = {{Start date and age|1966}}
|releasedate  = 
|discontinued = 
|cpu          = [[Transistor computer|Transistor]]<ref>{{cite book |last1=Laws |first1=United States Congress Senate Committee on the Judiciary Subcommittee to Investigate the Administration of the Internal Security Act and Other Internal Security |title=Terroristic Activity: Hearings Before the Subcommittee to Investigate the Administration of the Internal Security Act and Other Internal Security Laws of the Committee on the Judiciary, United States Senate, Ninety-third Congress, Second Session ... |date=1975 |publisher=U.S. Government Printing Office |page=513 |url=https://books.google.com/books?id=hNZNk-HAShgC&q=%22XDS-940+computer+is+a+second+generation+computer%22 |language=en|quote=(...) XDS-940 computer is a second generation computer (...)}}</ref> based custom 24-bit CPU
|memory       = 16 and 64 kilowords of 24 bits + parity, additional 4.5&nbsp;MB swap<ref name=stan68/>
|graphics     = Instructions of beam motion, character writing, etc, 20 characters per second. 1000-character terminals with 875-line screen.<ref name=stan68/>
|sound        =
|connectivity = Paper tape, line printer, modem
|storage      = 96&nbsp;MB at 117&nbsp;kB/s<!--(24*40000)/(8*1024)-->, [[Hard disk drive performance characteristics#Access time|access&nbsp;time]] 85&nbsp;ms<ref name=stan68/>
|os           = SDS 940 Time-Sharing System, originally the [[Berkeley Timesharing System]]
|unitssold    = 60
|price        = <!--{{USD|....}} (approx. ${{Inflation|US|....|1965|r=-2|fmt=c}} today)-->
|predecessor  = 
|successor    = 
}}
The '''SDS 940''' was [[Scientific Data Systems]]' (SDS) first machine designed to directly support [[time-sharing]]. The 940 was based on the [[SDS 930]]'s [[24-bit]] [[Central processing unit|CPU]], with additional circuitry to provide [[protected memory]] and [[virtual memory]].

It was announced in February 1966 and shipped in April, becoming a major part of [[Tymshare]]'s expansion during the 1960s. The influential [[SRI International|Stanford Research Institute]] [[NLS (computer system)|"oN-Line System"]] (NLS) was demonstrated on the system. This machine was later used to run [[Community Memory]], the first [[bulletin board system]].

After SDS was acquired by [[Xerox]] in 1969 and became Xerox Data Systems, the SDS 940 was renamed as the '''XDS 940'''.

==History==
The design was originally created by the [[University of California, Berkeley]] as part of their [[Project Genie]] that ran between 1964 and 1969. Genie added [[memory management]] and controller logic to an existing [[SDS 930]] computer to give it [[Page (computer memory)|page-mapped]] [[virtual memory]], which would be heavily copied by other designs. The 940 was simply a commercialized version of the Genie design and remained backwardly compatible with their earlier models, with the exception of the 12-bit [[SDS 92]].

Like most systems of the era, the machine was built with a bank of [[core memory]] as the primary storage, allowing between 16 and 64 kilowords. Words were [[24 bit]]s plus a [[parity bit]].<ref name="to"/>  This was backed up by a variety of secondary storage devices, including a 1376 kword drum in Genie, or [[hard disk]]s in the SDS models in the form of a drum-like 2097 kword "fixed-head" disk or a {{val|16384|u=kword}} traditional "floating-head" model. The SDS machines also included a [[paper tape]] punch and reader, [[line printer]], and a real-time clock.  They [[booting|bootstrapped]] from paper tape.

A file storage of 96&nbsp;MB were also attached. The [[line printer]] used was a Potter Model HSP-3502 chain printer with 96 printing characters and a speed of about 230 lines per minute.<ref name=stan68>{{cite web
|title=A research center for augmenting human intellect
|date=December 1968
|access-date=2016-04-19
|url=https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/Archive/ResearchCenter1968/ResearchCenter1968.html
|archive-date=2020-02-20
|archive-url=https://web.archive.org/web/20200220043259/https://web.stanford.edu/dept/SUL/library/extra4/sloan/mousesite/Archive/ResearchCenter1968/ResearchCenter1968.html
|url-status=dead
}}</ref>

It Sent The First Message On [[ARPANET]], "lo" before [[crashing]]. the original message was "login"

==Software system==
The [[operating system]] developed at Project Genie was the [[Berkeley Timesharing System]].<ref name="to">{{cite book |title= SDS 940 Time-Sharing System Technical Manual |work= SDS 90 11 16A |date= November 1967 |publisher= Scientific Data Systems |location= Santa Monica, California |url= http://bitsavers.org/pdf/sds/9xx/940/901116A_940_TimesharingTechMan_Nov67.pdf }}</ref>
By August 1968 a version 2.0 was announced that was just called the "SDS 940 Time-Sharing System".<ref name="soft68">{{cite book |title= SDS 940 Time-Sharing System (Version 2.0) Technical Manual |work= SDS 90 11 16B |date= August 1968 |publisher= Scientific Data Systems |location= Santa Monica, California |url= http://bitsavers.org/pdf/sds/9xx/940/901116B_940_TimesharingTechMan_Aug68.pdf }}</ref>
As of 1969, the XDS 940 software system consisted of the following:
* Time-Sharing Monitor (what is now usually called a [[kernel (operating system)|kernel]])<ref name="soft68"/>
* Time-Sharing Executive (what is now usually called a [[command-line interface]])<ref name="soft68"/>
* [[CAL (programming language)|CAL]], the Conversational Algebraic Language<ref>Butler Lampson (but without attribution), [https://archive.org/stream/bitsavers_sds9xx9409un67_2820101/901114A_940_CAL_RefMan_Jun67#page/n1/mode/1up CAL Reference Manual for SDS 940 Time-Sharing Computer System], Scientific Data Systems, June 1967.</ref>
* [[QED (text editor)|QED]], a text editor<ref>(without attribution), [https://archive.org/stream/bitsavers_sds9xx9409an69_1668444/901112B_940_QED_RefMan_Jan69#page/n1/mode/1up QED Reference Manual for SDS 940 Time-Sharing Computer Systems], Preliminary Edition, Scientific Data Systems, Jan. 1969.</ref>
* [[Fortran IV]]
* [[BASIC]]

The minimal configuration required to run the Software System included (partial list):
* Two 16-kword core-memory modules (with multiple access).<ref name="soft68op">{{cite book |title= SDS 940 Theory of Operation Technical Manual |work= SDS 98 01 26A |date= March 1967 |publisher= Scientific Data Systems |location= Santa Monica, California |url= http://bitsavers.org/pdf/sds/9xx/980126A_940_TheoryOfOperation_Mar67.pdf }}</ref>
* Two rapid-access disc (RAD) storage units and couplers (just under 4M character capacity each); optionally two more could be connected
* [[disk drive|Disc file]] and coupler, with 67M characters of storage
* [[Magnetic tape]] control unit and two magnetic-tape transports (controller supports up to 8)
* [[Asynchronous communication]] controller(s), supporting up to 64 [[teletypewriter]] lines each

Additional software was available from the XDS Users' Group Library, such as a [[string (computer science)|string]]-processing system, "SYSPOPs" (system programmed operators, which allow access to system services), [[CAL (Joss family)|CAL]] (Conversational Algebraic Language, a dialect of [[JOSS]]), [[QED (text editor)|QED]] (a text editor), TAP (Time-sharing Assembly Program, an [[Assembly language#Assembler|assembler]]), and [[Dynamic debugging technique|DDT]], a debugging tool.

A [[cathode-ray tube]] display with 26 lines that operated DDT loader-[[debugger]] that were originally designed to operate from a [[Teleprinter|teletype terminal]] were also available.<ref name=stan68/>

==Notable installations==
[[Butler Lampson]] estimated that about 60 of the machines were sold.<ref>{{cite web |title=Systems |author= Butler Lampson |author-link= Butler Lampson |publisher= Microsoft Research |url= http://research.microsoft.com/en-us/um/people/blampson/Systems.html#SDS940 |access-date= April 16, 2011 }}</ref>

* The major customer was [[Tymshare]], who used the system to become the USA's best known commercial timesharing service in the late 1960s. By 1972 Tymshare alone had 23 systems in operation.<ref>{{cite web |title= Timesharing as a Business |publisher= [[Computer History Museum]]  |url= http://www.computerhistory.org/revolution/mainframe-computers/7/181 |access-date= April 17, 2011 }} (includes pictures)</ref>
* [[Comshare]], Inc, of [[Ann Arbor, Michigan]], was the second most important corporate customer. Tymshare, Comshare and [[UC Berkeley]] collaborated in much of the operating system development for the SDS 940.
* [[Douglas Engelbart]]'s [[Augmentation Research Center]] (ARC) used an SDS 940 for their [[NLS (computer system)|oN-Line System]], more commonly known as NLS.<ref>{{cite book
   | last        = Markoff
   | first       = John
   | title       = What the Dormouse Said: How the Sixties Counterculture Shaped the Personal Computer Industry
   | year        = 2005
   | publisher   = Penguin Group
   | location    = New York
   | isbn        = 978-1-1012-0108-4
   | edition     = E-book
   | page        = 240
   | chapter     = 5 Dealing Lightning With Both Hands
   | quote       = E-book pages are approximate due device and fonts used
}}</ref>  It was with this computer that he gave [[The Mother of All Demos]] in December 1968, heralding many of the concepts associated with personal computing today.<ref>{{cite news
 |last        = Metz
 |first       = Cade
 |url         = https://www.theregister.co.uk/2008/12/11/engelbart_celebration/
 |title       = The Mother of All Demos — 150 years ahead of its time
 |date        = 2008-12-11
 |work        = The Register
 |access-date  = 2011-01-24
 |location    = London
 |archive-url  = https://web.archive.org/web/20131203033009/http://www.theregister.co.uk/2008/12/11/engelbart_celebration/
 |archive-date = 2013-12-03
 |url-status     = live
 }}</ref>
* The first host connected to the [[ARPANET]] was an SDS 940 at [[SRI International|SRI]] in October, 1969.<ref>{{cite web |last1=Crandall |first1=Rick |title=SDS 940 Timesharing Computer |url=http://rickcrandall.net/article3.php |website=Rick Crandall |access-date=23 December 2015 |url-status=dead |archive-url=https://web.archive.org/web/20151224104328/http://rickcrandall.net/article3.php |archive-date=24 December 2015 }}</ref>
* A [[San Francisco]] counterculture community action group called Resource One and located in ''Project One'' used a donated surplus XDS 940 as described in ''[[Rolling Stone]]'' magazine in 1972.<ref>{{cite magazine |title= Spacewar: Fanatic Life and Symbolic Death Among the Computer Bums |author= Stewart Brand |author-link= Stewart Brand |magazine= [[Rolling Stone]] |date= December 7, 1972 |url= http://www.wheels.org/spacewar/stone/rolling_stone.html |access-date= April 16, 2011}}</ref>
* The [[Community Memory]] project served as an early electronic [[bulletin board system]].<ref>{{cite web |title= Community Memory: 1972–1974, Berkeley and San Francisco, California |publisher= [[The WELL]]: Whole Earth 'Lectronic Link |url= http://www.well.com/~szpak/cm/index.html |access-date= April 17, 2011 |archive-date= November 17, 2016 |archive-url= https://web.archive.org/web/20161117031011/http://www.well.com/~szpak/cm/index.html |url-status= dead }}</ref>

==See also==
*[[SDS Sigma series]]
*[[SDS 9 Series]]

==References==
{{Reflist}}

<!-- ==Further reading==
*[[Scientific Data Systems|Xerox Data Systems]], ''XDS 940 Computer'' (1969) what about it?? Is this a document? -->

==External links==
* {{cite web |title= SDS 940 Computer - console |publisher= [[Computer History Museum]]  |url= http://www.computerhistory.org/revolution/mainframe-computers/7/181/730?position=0 |access-date= April 17, 2011 }} (pictures)
*[http://bitsavers.org/bits/SDS/9xx/ Software archive]

[[Category:Mainframe computers]]
[[Category:Scientific Data Systems]]
[[Category:Time-sharing]]
[[Category:24-bit computers]]