The story of how MS-DOS became the industry standard for the 16-bit business computers at the expense of Digital Research’s CP/M is somewhat of a legend among fans of computing history. The event has been described in books, articles and documentaries, with most of them focusing on entertaining details such as corporate drama, back-stabbing and nepotism1.

Some of the more serious accounts mention one important detail of the story: DRI was late with the port of the CP/M to the Intel 8086. When IBM representatives visited in August of 1980, looking for an operating system for their upcoming PC, only the 8-bit version of CP/M could be demonstrated. IBM eventually turned to Microsoft and selected what became MS‑DOS.

In this article, we will examine why CP/M‑86 was delayed and, in the end, speculate how much that delay actually mattered.