Turn your Apple into the world's most versatile personal computer.

This is a real curiosity from Microsoft which shows how different the company was before the power of its coming hegemony with Intel and its own MS-DOS - and later Windows operating system - corrupted it for the next three decades.

It's for what was the company's first ever hardware product - a Z80 board for the Apple II, which gave the Apple II support for the CP/M operating system.

That's interesting on two levels: firstly, Microsoft's MS-DOS was actually based upon a copy of CP/M that had been cloned by Seattle Computer Products and sold to Microsoft, which it called PC-DOS and sold to IBM as the operating system for its new IBM PC, launched this year. 

In turn, MS-DOS and the IBM PC would sideline pretty much every other microcomputer ecosystem, contributing to the death of Digital Research - Gary Kildall's company which had created CP/M way back in 1973.

And secondly, one of the few companies that did hang on in the face of what became known as the WinTel alliance (Windows/Intel) was, ironically, Apple - and the two would become sometimes bitter enemies.

So here is Microsoft's own SoftCard - helping both Digital Research and Apple. 

However, it wasn't altruism but a question of software portability that led to Paul Allen suggesting that Microsoft develop a Z80 board, as Microsoft wanted a way to port its extensive range of Intel 8080/Z80 systems software onto the Apple and its growing user base.

The alternative would have been to re-write all its software for the MOS Technology 6502 that the Apple used, but that would be very much "re-inventing the wheel", according to Vern Raburn of Microsoft Consumer Products[source: "Developed by Microsoft", Letters, Computerworld, October 20th 1980, p. 37]. 

Producing a Z80 card for the Apple II sidestepped this and allowed countless hundreds of CP/M and Z80 software houses to now target the Apple ecosystem.