Z-80 SoftCard

The Z-80 SoftCard is a plug-in card supplied by Microsoft for use with the Apple II personal computer, which does not have a Z80-compatible processor and cannot run CP/M. It has a Zilog Z80 CPU plus some 74LS00 series TTL chips to adapt that processor's bus to the Apple bus. The card was eventually renamed the Microsoft SoftCard.

Introduced in 1980 as Microsoft's first hardware product, it enables the Apple II to run the Digital Research CP/M operating system—then the industry-standard operating system for running business software—and many compilers and interpreters for several high-level languages on microcomputers. CP/M, one of the earliest cross-platform operating systems, is easily adaptable to a wide range of auxiliary chips and peripheral hardware, but it requires an Intel 8080-compatible CPU, which the Zilog Z80 is, but which the Apple's CPU, the MOS Technology 6502, is not.

This CP/M capability conferred by the Z80 SoftCard transformed the Apple II into a viable platform for running a much broader range of business software applications than had been possible until then.

The SoftCard was Paul Allen's idea and was developed by Tim Paterson of Seattle Computer Products (SCP) and Bill Gates and Don Burtis of Microsoft, after SCP developed the initial prototypes. Microsoft received most of its revenue from selling language compilers and interpreters for CP/M systems, which was before Microsoft's MS-DOS operating system (for Intel 8086-compatible processors as used by the IBM PC and other microcomputers) was introduced and became the company's best-selling product. A copy of the Microsoft BASIC programming language was included in the Softcard package. Unsure whether the card would sell, Microsoft first demonstrated it publicly at the West Coast Computer Faire in March 1980.

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