Systems Concepts

From Academic Kids

Systems Concepts (now the SC Group) is a company focused on making hardware products related to the DEC PDP-10 series of computers. One of its major products was the SA-10, an interface which allowed PDP-10s to be connected to disk and tape drives designed for use with the channel interfaces of IBM mainframes.

Later, Systems Concepts attempted to produce a compatible replacement for the DEC PDP-10 computers. This project was a legendary tragic failure, the archetypal Hacker Dream Gone Wrong. Mars was the code name for a family of PDP-10-compatible computers built by Systems Concepts, including the initial SC-30M, the smaller SC-25, and the slower SC-20. These machines were marvels of engineering design; although not much slower than the unique Foonly F-1, they were physically smaller and consumed less power than the much slower DEC KS10 or Foonly F-2, F-3, or F-4 machines. They were also completely compatible with the DEC KL10, and ran all KL10 binaries (including the operating system) with no modifications at about 2-3 times faster than a KL10.

When DEC cancelled the Jupiter project in 1983, Systems Concepts should have made a bundle selling their machine into shops with a lot of software investment in PDP-10s, and in fact their spring 1984 announcement generated a great deal of excitement in the PDP-10 world. TOPS-10 was running on the Mars by the summer of 1984, and TOPS-20 by early fall. Unfortunately, the hackers running Systems Concepts were much better at designing machines than at mass producing or selling them; the company allowed itself to be sidetracked by a bout of perfectionism into continually improving the design, and lost credibility as delivery dates continued to slip. They also overpriced the product ridiculously; they believed they were competing with the KL10 and VAX 8600 and failed to reckon with the likes of Sun Microsystems and other hungry startups building workstations with power comparable to the KL10 at a fraction of the price. By the time SC shipped the first SC-30M to Stanford in late 1985, most customers had already made the traumatic decision to abandon the PDP-10, usually for VMS or Unix boxes. Nevertheless, a number of Mars computers were purchased by CompuServe, which depended on PDP-10s to run its online service and was eager to move to newer but fully-compatible systems. CompuServe's demand for the computers outpaced Systems Concepts' ability to produce them, so CompuServe licensed the design and built SC-designed computers itself.

SC later designed the SC-40, released in 1993, a faster follow-on to the SC-30M and SC-25. It can perform up to 8 times as fast as a DEC KL-10, and it also supports more physical memory, a larger virtual address space, and more modern input/output devices. These systems were also used at CompuServe.

Systems Concepts remains in business, having changed its name to the SC Group when it moved from California to Nevada some years ago.

External links

Description of SC-40 at SC Group website (

This article is based in part on an article from the jargon file. The jargon file is in the public domain.


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