SDS 930

The Scientific Data Systems SDS-930, was the first commercial computer series to use transistors (PNP).

It consisted of at least three standard (30 cu. ft.) cabinets, comprising the arithmetic and logic unit, at least 8,192 words (24-bit + simple parity) magnetic core memory (with a temperature gauge), and the IO unit. Sign magnitude integer mathematics was used instead of 2's complement.

A free-standing console was also provided, which included binary displays of the machine's registers and switches to boot and debug programs. User input was by a Model 35 ASR teletype unit and a high-speed paper tape reader (300 cps). Most systems included at least two magnetic tape drives, operating at up to 75 inches/second at 800 bpi. The normal variety of peripherals were also available, including magnetic drum units, card readers and punches, and an extensive set of analog-digital/digital-analog conversion devices. A graphic display using was also available, but remarkably it did not include a means of keyboard input.

The 930 was a typical small to medium scale scientific computer at the time. Speed was good for its cost, but with an integer add time of 3.5 microseconds, it was not in the same league as the scientific workhorses of the day (the CDC 6600, for example). A well equipped SDS-930 could easily exceed 10 cabinets and require a 300-500 sq. ft. climate controlled room. The price of such a system in 1966 would be in the neighborhood of $500K.

Programming languages available for SDS included FORTRAN II, ALGOL 60, and the assembly language known as Metasymbol. The FORTRAN system was very compact, having been designed and implemented by Digitek for SDS to compile and run in 4,096 word SDS 900 series machines. In order to be able to do anything useful in such small memory space, the compiler relied on an SDS architectural feature known as Proprammed Operators, or POPS. This consisted of a single bit in the instruction word that caused the machine to "mark place and branch" to the memory location equalling the instruction code plus 64. As a result, pseudo instructions could be programmatically defined and implemented yielding very compact special-purpose code. Both the compiler and runtime took advantage of this.

Towards the end of the SDS-930's market lifetime, a realtime operating system was introduced, and it included a FORTRAN IV compiler. Both the operating system and the compiler were a disaster, being anything but realtime and including so many bugs that it was virtually impossible to use them for any useful work.

930's were used for much important work and could be found at most of the major US government labs at the time, including Los Alamos. Early Flight simulators used the SDS-930, because of its hardware multiply circuitryand extensive expandable I/O modules. The machines were particularly well-suited to high-speed data acquisition and realtime analysis, as well as serving as the controller for analog systems.

ee also

SDS 940

External links

* [http://bitsavers.org/pdf/sds/9xx SDS 900-series documents at bitsavers.org]
* [http://www.andrews.edu/~calkins/profess/SDSigma7.htm#CH1 SDS and the 24 bit computers]
* [http://www.quadibloc.com/comp/cp0303.htm Real Machines with 24-bit and 48-bit words]
* [http://www.chac.org/chsds930.html Last known working SDS 930]