The S-100 bus or Altair bus, IEEE696-1983 (withdrawn), was an early computer bus designed in 1974 as a part of the Altair 8800. The S-100 bus was the first industry standard expansion bus for the microcomputer industry. S-100 computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The S-100 bus formed the basis for homebrew computers whose builders (e.g., the Homebrew Computer Club) implemented drivers for CP/M and MP/M. These S-100 microcomputers ran the gamut from hobbyist toy to small business workstation and were common in early home computers until the advent of the IBM PC (which some of them outperformed).

Architecture

The S-100 bus is a passive backplane of 100-pin printed circuit board edge connectors wired in parallel. Circuit cards measuring 5 × 10-inches serving the functions of CPU, memory, or I/O interface plugged into these connectors. The bus signal definitions closely follow those of an 8080 microprocessor system, since the Intel 8080 microprocessor was the first microprocessor hosted on the S-100 bus. The 100 lines of the S-100 bus can be grouped into four types: 1) Power, 2) Data, 3) Address, and 4) Clock and control.

S100 or S-100 can refer to: