MacMach

Mach decouples Unix from the kernel. MacMach boots the native Mach 3.0 microkernel, which runs 4.3BSD as one task and the entire Macintosh graphical environment and applications as another task. Mach's virtualization layer allows one computer and display to have BSD running the X Window System alongside unmodified Macintosh applications, such as Microsoft Excel and MacDraw. Support is limited to Motorola 68020 and Motorola 68030-based hardware with a paged memory management unit (PMMU), specifically select configurations of the Macintosh II, IIx, IIcx, IIci, IIfx, and SE/30.^[1]

CMU released the source code on CD-ROM in 1992 for approximately US$100 (equivalent to about $220 in 2024).^[2][3] Unlike the competing MachTen, which is a commercially supported product, MacMach is a research distribution with restrictive licensing.^[2][4][5] Because the system relies on the original 4.3BSD codebase, users are legally required to hold an AT&T UNIX System V source license.^[3] MacUser noted this restriction makes the system inaccessible to most general users.^[3]

Following the settlement of the USL v. BSDi lawsuit and the release of unencumbered 4.4BSD-Lite, the MacMach project was abandoned.^{[citation needed]} However, CMU had launched MacMach to support Macintosh II (alongside IBM) on the institution's new Andrew Project, a network-distributed and platform-independent personal computing platform, and Apple representatives indicated its experimental purposes and the unlikelihood of the company's commercial use of such an outside operating system.^[6]

In April 1994, CMU posted this to Usenet:

The people responsible for this port have been gone from CMU for several years and so the code and the distribution procedure have succumbed to software rot. The distribution always required an AT&T source license, plus there were futher restraints specified by Apple. As a result there was no way for us to pass the effort on to other parties.

Apple later redirected its microkernel efforts toward the OSF Research Institute for the development of MkLinux.