S-100 Bus Standard Adopted

Sol Libes
Byte Magazine

March 1983

The IEEE has finally adopted the S-100/IEEE-696 bus standard for microcomputer systems. This standard, which has been in the works for over three years (typical development time for an IEEE standard) and required the approval of four separate committees, is an important one because the S-100 bus is the most popular bus system used by microcomputer manufacturers. Currently close to 150 manufacturers make a total of over 500 different plug-in boards for S-100 systems. Hence, the standard will ensure a high degree of compatibility among different manufacturers' products.

Even more important, the standard provides for implementing future changes in the state of the art in microcomputer systems. The standard allows up to 16 megabytes of direct memory addressing, up to 64K I/O ports, up to 10 vectored interrupts, up to 16 masters, with a mix of up to 22 masters and slaves (including a frontpanel option), and the flexibility of configuring a system any way the user wishes.

Manufacturers have already introduced S-100 processor cards for half a dozen different 8-bit microprocessors (Intel's 8080 and 8085, Zilog's Z80, MOS Technology's 6502, and Motorola's 6800 and 6809) and seven different 16-bit microprocessors (TI's 9900, DEC's LSI-11, Intel's 8086 and 8088, Zilog's Z8000, Motorola's 68000, and National Semiconductor's 16032). More processor cards are expected.

The S-100 manufacturers lead the industry in implementing new technical developments. They were the first to introduce to the personal computer marketplace 16-bit systems; the CP/M, MS-DOS, OASIS, and Turbo-Dos operating systems; floppy-disk systems; hard-disk systems; virtual-disk systems; cache-memory systems; multiprocessing; and multiuser systems. In all probability they will continue to lead in the introduction of state-of-the-art features.

Credit for the development development of the S-100/IEEE-696 bus standard goes to George Morrow of Morrow Designs and Kels Elmquist of Ithaca Intersystems for drafting the original standard, and to Mark Garetz of Compupro who finalized the standard and piloted it through the committees to final adoption. It is expected that the standard will be published in a final form by the IEEE. To find out about receiving a copy, send a stamped, selfaddressed, business-size envelope to Mark Garetz, Compupro, Box 2355, Oakland Airport, CA 94614.

Copyright 1983