Apple CP / M
Apple CP / M was the CP / M version for the Apple II . In order to be able to use it, the computer must be equipped with a Z80 plug-in card.
Thanks to Visicalc, the Apple II quickly became a bestseller ; After many had only bought the device because of this world's first and initially only spreadsheet software, which was initially only available for Apple, the disillusionment soon followed: Thanks to the built-in BASIC interpreter, you could create your own smaller programs very quickly carry out calculations with Visicalc; A (really) good word processor or a database was searched in vain. They were available in the form of WordStar and dBASE , but only for the standard operating system at the time, CP / M , and that (and the programs for it) did not run on the Apple II because it contained a 6502 processor , CP / M and Back then, his programs only ran on 8080 processors or the upwardly compatible Z80 .
Since the Apple II offered enormous potential with its 50% market share at the time, many were working on expansion cards with such a processor on it, with which one could run CP / M and thus - for the conditions at the time - a huge number of programs on the Apple . The company Microsoft (then still written "Micro-Soft") won the race with their "SoftCard" said Additional card featuring a Z80 processor and the necessary glue logic contained to those in the other types of 6502-bus system of Apple integrate. The card came with a version of CP / M licensed by Digital Research . Microsoft had the hardware of the card developed by a third company, so their own work consisted primarily in the organization of the project and in marketing.
Microsoft's goal with the Softcard was actually to develop an additional customer base for their own CP / M-based interpreters and compilers for various programming languages, but most buyers did not purchase the card for programming, but primarily for various ready-made office software from other manufacturers to be able to use (e.g. dBASE from Ashton-Tate). Various replicas of the Softcard from other companies soon appeared.
A little later, more powerful Z80 cards came onto the market: A little later, Digital Research itself sold the so-called ALS card, with its own 64 KB main memory and a much faster clocked Z80 (6 MHz). However, this could no longer assert itself on the market against the established MS Softcard. Others brought Z80 cards onto the market too: z. B. Applied Engineering. The basis for the speed record for the Z80 cards was laid by the PCPI applicard: a retro project by Alex Freed around 2009 resulted in a clone of the applicard originally clocked at 6 MHz under the name Freed-card. Theoretically, this could be operated at up to 20 MHz. In order to be able to assess this, you have to know that the original Microsoft softcard was clocked at 4 MHz, but due to the timeshare with the 6502, it could only use 50% of the clocks itself. This only brought the softcard to an equivalent of 2 MHz. For every card that is not directly compatible with the softcard, variants of the operating system with a correspondingly adapted BIOS were created.
Unknown to most users and critics of Microsoft software today, but no less interesting, is the fact that this card was the main source of income for Microsoft for a good two years (1979–1981) when the young company was not yet operating systems and office applications, but rather practically only offered compilers and interpreters for different programming languages, which could only be brought to the buyer in moderate numbers. Based on the experience this company had with home computers and the appropriate software, IBM contacted Microsoft in 1980 and asked for an operating system in addition to BASIC for the IBM PC, which was currently being developed .