A 100-pin bus specification used in the design of computers built around the Intel 8080 and Zilog Z-80 microprocessors. System designs using the Motorola 6800, 68000, and Intel iAPx86 family of microprocessors have also been built around the S-100 bus. S-100 computers were extremely popular with early computer enthusiasts. They had an open architecture, which permitted the configuration of systems with a wide range of add-on expansion boards.