Tanenbaum originally developed MINIX for compatibility with the IBM PC and IBM PC/AT microcomputers available at the time. MINIX 1.5, released in 1991, included support for MicroChannel IBM PS/2 systems and was also ported to the Motorola 68000 and SPARC architectures, supporting the Atari ST, Commodore Amiga, Apple Macintosh and Sun SPARCstation computer platforms. There were also unofficial ports to Intel 386 PC compatibles (in 32-bit protected mode), National Semiconductor NS32532, ARM and INMOS transputer processors. Meiko Scientific used an early version of MINIX as the basis for the MeikOS operating system for its transputer-based Computing Surface parallel computers. A version of MINIX running as a user process under SunOS was also available.
Demand for the 68k-based architectures waned, however, and MINIX 2.0, released in 1997, was only available for the x86 and Solaris-hosted SPARC architectures. It was the subject of the second edition of Tanenbaum's textbook, co-written with Albert Woodhull and was distributed on a CD-ROM included with the book. MINIX 2.0 added POSIX.1 compliance, support for 386 and later processors in 32-bit mode and replaced the Amoeba network protocols included in MINIX 1.5 with a TCP/IP stack. Unofficial ports of MINIX 2.0.2 to the 68020-based ISICAD Prisma 700 workstation and the Hitachi SH3-based HP Jornada 680/690 PDA were also developed.
MINIX 3 was publicly announced on 24 October 2005 by Andrew Tanenbaum during his keynote speech on top of the ACM Symposium Operating Systems Principles conference. Although it still serves as an example for the new edition of Tanenbaum and Woodhull's textbook, it is comprehensively redesigned to be "usable as a serious system on resource-limited and embedded computers and for applications requiring high reliability." MINIX 3 currently supports only IA-32 architecture PC compatible systems. It is available in a Live CD format that allows it to be used on a computer without installing it on the hard drive, and in versions compatible with hardware emulation/virtualization systems, including Bochs, Qemu, VMware Workstation/Fusion, and Microsoft Virtual PC.
Version 3.1.2 was released 8 May 2006. It contains X11, emacs, vi, cc, gcc, perl, python, ash, bash, zsh, , ssh, , pine, and over 400 other common UNIX utility programs. With the addition of X11, this version marks the transition away from a text-only system. Another feature of this version, which will be improved in future ones, is the ability of the system to withstand device driver crashes, and in many cases having them automatically replaced without affecting running processes. In this way, MINIX is self-healing and can be used in applications demanding high reliability.
These accusations were rebutted universally - in particular by Andrew Tanenbaum, who strongly criticised Kenneth Brown and published a long rebuttal on his own personal website.
When free/open source Unix-like operating systems such as Linux and 386BSD became available in the early 1990s many volunteer software developers abandoned MINIX in favour of these. In April 2000, MINIX became free/open source software under a permissive free software licence, but by this time other operating systems had surpassed its capabilities, and it remained primarily an operating system for students and hobbyists.