SDS 940
Encyclopedia
The SDS 940 was Scientific Data Systems
' (SDS) first machine designed to support time sharing directly, and was based on the SDS 930
's 24-bit
CPU built primarily of integrated circuits. It was announced in February 1966 and shipped in April, becoming a major part of Tymshare
's expansion during the 1960s. The influential Stanford Research Institute "oN-Line System"
(NLS) was demonstrated on the system.
After SDS was acquired by Xerox
in 1969 and became Xerox Data Systems, the SDS 940 was renamed as the XDS 940.
as part of their Project Genie
that ran between 1964 and 1965. Genie added memory management
and controller logic to an existing SDS 930
computer to give it 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 bits plus a parity bit
.
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 16777 kWord traditional "floating head" model. The SDS machines also included a paper tape punch and reader, line printer
, and a real-time clock. They bootstrapped
from paper tape.
developed at Project Genie was the Berkeley Timesharing System
.
By August 1968 a version 2.0 was announced that was just called the "SDS 940 Time-Sharing System".
As of 1969, the XDS 940 Software System consisted of the following:
The minimum configuration required to run the Software System included (partial list):
Additional software was available from the XDS Users' Group Library, such as a string
processing system, "SYSPOPs" (system programmed operators, which allow access to system services), CAL
(Conversational Algebraic Language, a dialect of JOSS
), QED
(a text editor), TAP (Time-sharing Assembly Program, an assembler), and DDT
, a debugging tool.
estimated about 60 of the machines were sold.
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.
A San Francisco
counterculture community action group called Project One used a free surplus XDS 940 as described in Rolling Stone magazine
in 1972.
The Community Memory
project served as an early electronic bulletin board system
.
Scientific Data Systems
Scientific Data Systems, or SDS, was an American computer company founded in September 1961 by Max Palevsky, a veteran of Packard Bell and Bendix, along with eleven other computer scientists. SDS was an early adopter of integrated circuits in computer design and the first to employ silicon...
' (SDS) first machine designed to support time sharing directly, and was based on the SDS 930
SDS 930
The SDS 930 was a commercial computer using bipolar junction transistors sold by Scientific Data Systems.It was announced in December 1963, with first installations in June 1964.-Description:An SDS 930 system consisted of at least three standard The SDS 930 was a commercial computer using bipolar...
's 24-bit
24-bit
Notable 24-bit machines include the ICT 1900 series and the Harris H series.The IBM System/360, announced in 1964, was a popular computer system with 24-bit addressing and 32-bit general registers and arithmetic...
CPU built primarily of integrated circuits. It was announced in February 1966 and shipped in April, becoming a major part of Tymshare
Tymshare
Tymshare, Inc. was headquartered in Cupertino, California from 1964 to 1984.It was a well-known timesharing service and third-party hardware maintenance company throughout its history and competed with companies such as Four Phase, Compuserve, and Digital Equipment Corporation...
's expansion during the 1960s. The influential Stanford Research Institute "oN-Line System"
NLS (computer system)
NLS, or the "oN-Line System", was a revolutionary computer collaboration system designed by Douglas Engelbart and implemented by researchers at the Augmentation Research Center at the Stanford Research Institute during the 1960s...
(NLS) was demonstrated on the system.
After SDS was acquired by Xerox
Xerox
Xerox Corporation is an American multinational document management corporation that produced and sells a range of color and black-and-white printers, multifunction systems, photo copiers, digital production printing presses, and related consulting services and supplies...
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, BerkeleyUniversity of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
as part of their Project Genie
Project Genie
Project Genie was a computer research project started in 1964 at the University of California, Berkeley.It produced an early time-sharing system including the Berkeley Timesharing System, which was then commercialized as the SDS 940.-History:...
that ran between 1964 and 1965. Genie added memory management
Memory management
Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed. This is critical to the computer system.Several...
and controller logic to an existing SDS 930
SDS 930
The SDS 930 was a commercial computer using bipolar junction transistors sold by Scientific Data Systems.It was announced in December 1963, with first installations in June 1964.-Description:An SDS 930 system consisted of at least three standard The SDS 930 was a commercial computer using bipolar...
computer to give it page-mapped virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
, 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 bits plus a parity bit
Parity bit
A parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
.
This was backed up by a variety of secondary storage devices, including a 1376 kWord drum in Genie, or hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
s in the SDS models in the form of a drum-like 2097 kWord "fixed head" disk or a 16777 kWord traditional "floating head" model. The SDS machines also included a paper tape punch and reader, line printer
Line printer
The line printer is a form of high speed impact printer in which one line of type is printed at a time. They are mostly associated with the early days of computing, but the technology is still in use...
, and a real-time clock. They bootstrapped
Booting
In computing, booting is a process that begins when a user turns on a computer system and prepares the computer to perform its normal operations. On modern computers, this typically involves loading and starting an operating system. The boot sequence is the initial set of operations that the...
from paper tape.
Software System
The operating systemOperating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
developed at Project Genie was the Berkeley Timesharing System
Berkeley Timesharing System
The Berkeley Timesharing System was a pioneering time-sharing operating system implemented between 1964 and 1967 at the University of California, Berkeley...
.
By August 1968 a version 2.0 was announced that was just called the "SDS 940 Time-Sharing System".
As of 1969, the XDS 940 Software System consisted of the following:
- Time-Sharing Monitor roughly what is now usually called a kernelKernel (computing)In computing, the kernel is the main component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources...
- Time-Sharing Executive roughly what is now usually called a command-line interfaceCommand-line interfaceA command-line interface is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks...
- Fortran IV
- BASICBASICBASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
The minimum configuration required to run the Software System included (partial list):
- Two 16K-word core memory modules (with multiple access)".
- Two rapid-access disc (RAD) storage units and couplers (just under 4M character capacity each); optionally two more could be connected
- Disc file and coupler, with 67M characters of storage
- Magnetic tapeMagnetic tapeMagnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...
control unit and two magnetic tape transports (controller supports up to 8) - Asynchronous communicationAsynchronous communicationIn telecommunications, asynchronous communication is transmission of data without the use of an external clock signal, where data can be transmitted intermittently rather than in a steady stream. Any timing required to recover data from the communication symbols is encoded within the symbols...
controller(s), supporting up to 64 teletypewriter lines each
Additional software was available from the XDS Users' Group Library, such as a string
String (computer science)
In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....
processing system, "SYSPOPs" (system programmed operators, which allow access to system services), CAL
CAL programming language
CAL was a programming language and system designed and developed by Butler Lampson at Berkeley in 1967.The design of CAL was based on JOSS but had new features and was implemented on the SDS 940. Lampson states that "many of its techniques were adopted by Tymshare for their interactive SuperBasic...
(Conversational Algebraic Language, a dialect of JOSS
JOSS
JOSS was one of the very first interactive, time sharing programming languages.JOSS I, developed by J. Clifford Shaw at RAND was first implemented, in beta form, on the JOHNNIAC computer in May 1963...
), QED
QED (text editor)
QED is a line-oriented computer text editor that was developed by Butler Lampson and L. Peter Deutsch for the Berkeley Timesharing System running on the SDS 940. It was implemented by L...
(a text editor), TAP (Time-sharing Assembly Program, an assembler), and DDT
Dynamic debugging technique
Dynamic Debugging Technique, or DDT, was the name of several debugger programs originally developed for DEC hardware, initially known as DEC Debugging Tape because it was distributed on paper tape. The name is a pun on the insecticide Dynamic Debugging Technique, or DDT, was the name of several...
, a debugging tool.
Notable installations
Butler LampsonButler Lampson
Butler W. Lampson is a renowned computer scientist.After graduating from the Lawrenceville School , Lampson received his Bachelor's degree in Physics from Harvard University in 1964, and his Ph.D...
estimated about 60 of the machines were sold.
The major customer was Tymshare
Tymshare
Tymshare, Inc. was headquartered in Cupertino, California from 1964 to 1984.It was a well-known timesharing service and third-party hardware maintenance company throughout its history and competed with companies such as Four Phase, Compuserve, and Digital Equipment Corporation...
, 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.
A San Francisco
San Francisco, California
San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...
counterculture community action group called Project One used a free surplus XDS 940 as described in Rolling Stone magazine
Rolling Stone
Rolling Stone is a US-based magazine devoted to music, liberal politics, and popular culture that is published every two weeks. Rolling Stone was founded in San Francisco in 1967 by Jann Wenner and music critic Ralph J...
in 1972.
The Community Memory
Community Memory
Community Memory was the first public computerized bulletin board system. Established in 1973 in Berkeley, California, it used an SDS 940 timesharing system in San Francisco connected via a 110 baud link to a teleprinter at a record store in Berkeley to let users enter and retrieve messages...
project served as an early electronic bulletin board system
Bulletin board system
A Bulletin Board System, or BBS, is a computer system running software that allows users to connect and log in to the system using a terminal program. Once logged in, a user can perform functions such as uploading and downloading software and data, reading news and bulletins, and exchanging...
.