SDS 940
| Industry | Computer hardware, Time-sharing systems |
|---|---|
| Headquarters | United States |
| Products | SDS 940 |
The SDS 940 marked Scientific Data Systems' initial foray into hardware explicitly engineered to facilitate time-sharing. Its architecture was derived from the 24-bit CPU of the SDS 930, enhanced with additional components to implement protected memory and virtual memory. Introduced in February 1966 and delivered starting April of the same year, it significantly contributed to the growth of Tymshare throughout the 1960s. The influential Stanford Research Institute showcased its "oN-Line System" (NLS) on this platform. It also hosted Community Memory, recognized as the pioneering bulletin board system. Following SDS’s acquisition by Xerox in 1969, which led to the formation of Xerox Data Systems, the SDS 940 was rebranded as the XDS 940.
History
The genesis of the SDS 940 traces back to University of California, Berkeley's Project Genie (1964–1969), which upgraded an existing SDS 930 unit by integrating page-mapped virtual memory and sophisticated memory management techniques. This commercial model preserved compatibility with prior systems except for the 12-bit SDS 92.
Its primary memory comprised core modules ranging from 16 to 64 kilowords of 24-bit words, each equipped with parity checking. Secondary storage options varied, including a drum device (holding 1376 kwords in Genie), "fixed-head" disks resembling drums (2097 kwords), and conventional "floating-head" disk drives offering up to 16,384 kwords. Peripheral devices encompassed paper tape punch and reader, line printers, and a real-time clock; system bootstrapping was performed via paper tape.
File storage capacity extended up to 96 MB. The line printer used was a Potter Model HSP-3502 chain printer capable of producing approximately 230 lines per minute with support for 96 characters per line.
Significantly, the SDS 940 transmitted the inaugural message over the ARPANET, sending "lo" before crashing—the intended transmission was "login."
Software system
The operating system crafted under Project Genie was named the Berkeley Timesharing System. By August 1968, version 2.0 had been released under the designation "SDS 940 Time-Sharing System."
In 1969, the XDS 940's software package comprised:
- Time-Sharing Monitor (the core kernel)
- Time-Sharing Executive (command-line interface)
- CAL (Conversational Algebraic Language)
- QED (text editor)
- Fortran IV
- BASIC
The minimal hardware setup required to operate this system included:
- Two core-memory modules of 16 kilowords each with concurrent access capability
- Two rapid-access disk (RAD) units, each with approximately four million characters capacity, expandable as needed
- Disk file and coupler providing up to 67 million characters of storage
- Magnetic tape controller managing up to eight tape transports
- Asynchronous communication controllers supporting up to 64 teletype terminals each
Supplementary software available from the XDS Users' Group Library included string-processing utilities, system programmed operators ("SYSPOPs"), various CAL dialects, the QED editor, TAP assembler, and DDT debugging tools.
A cathode-ray tube display featuring 26 lines was provided for operating the DDT loader-debugger, originally designed for teletype terminal use.
Notable installations
Butler Lampson estimated total sales at around 60 units.
- The principal client was Tymshare, which emerged as America's foremost commercial timesharing provider during the late 1960s. By 1972, Tymshare managed a fleet of 23 such systems.
- The second largest corporate customer was Comshare, Inc., located in Ann Arbor, Michigan. Tymshare, Comshare, and UC Berkeley collaborated closely on advancing the SDS 940 operating system.
- The SDS 940 served as the computing platform for Douglas Engelbart's Augmentation Research Center (ARC) running their oN-Line System (NLS). This machine supported Engelbart’s groundbreaking December 1968 demonstration that introduced numerous concepts foundational to modern personal computing.
- The first host connected to the ARPANET network was an SDS 940 stationed at SRI in October 1969.
- The San Francisco countercultural collective Resource One utilized a surplus XDS 940 donated for Project One, as reported by Rolling Stone magazine in 1972.
- The SDS 940 powered the Community Memory initiative, one of the earliest electronic bulletin board systems.
See also
External links
- SDS 940 Computer - console at the Computer History Museum (photographs)
- Software repository