Mach had an unusually large amount of fanfare starting from its introduction at USENIX circa 1985 up to the mid-90s. It was envisioned as a generic resource multiplexer to build all sorts of platforms on top of, and particularly for emulating Unix. You had single-server Unixes like Lites and OSF&#x2F;1 (the latter sold commercially by DEC as Tru64 UNIX), plus multi-server systems like Mach-US, MASIX, MK++ (for high assurance) and GNU Hurd.<p>In the late 80s, the Open Software Foundation (OSF) was founded as a consortium of seven major tech companies spearheaded by DEC to standardize Unix in response to AT&amp;T and Sun&#x27;s adoption of SVR4. They adopted Mach as part of this and ended up extending it to add locksets, semaphores and resource ledgers. MkLinux was then a joint effort in 1996 by Apple and the OSF to both have Linux on the PPC and exploit Mach features in the single-server emulation.<p>As such, the history is convoluted. It&#x27;s not that Mach is so great, but rather that circumstances made it creep in various places.