3 ms·

> Of course, there’s also the Unix foundation of NeXTstep, which importance cannot be understated, especially during the rise of the Unix workstation in the 198

> Of course, there’s also the Unix foundation of NeXTstep, which importance cannot be understated, especially during the rise of the Unix workstation in the 1980s and the 1990s. This gave NeXTstep (and later Mac OS X) a user base who could take advantage of PARC-inspired environments while at the same time being able to take advantage of the vast Unix ecosystem. A UNIX ecosystem built on top of Mach. Both macOS and iOS continue to use a BSD-derived POSIX compatibility layer on top of a Mach microkernel - just like NeXTSTEP did.

iohead 3y ago
No, not quite. The macOS/iOS kernel is extremely Frankenstein-y (not meant in a derogatory way), with the majority of codebase being extremely Apple-specific, and bits and pieces originally taken from Mach and BSD. In particular, there is no microkernel, and there never was. Mach itself was never used as a true microkernel in a commercial setting, with the first such implementation--Mach 3--showing significant real-life performance problems. As such, there is no "BSD on top of a Mach microkernel". It is and has always been a fully monolithic kernel with some subsystems originally derived from Mach (Open Group's Mk 7.3), some from BSD (FreeBSD 5), and the rest developed in-house over the years. Even the layerings aren't always clean, with "on top of" often morphing into "alongside" or "intertwined with".
- detourdog 3y ago
  What is interesting about Mach to me. Is that now 40 years later it's returning too it's roots of hosting multiple OS's on a single hardware architecture. Apple being able to design to M series chips to match Mach's paper over Mach's deficiencies and leverage it's strength I find very exciting. Originally it was meant to be the foundation computing layer for a campus full of devices.
detourdog 3y ago
The BSD choice dates back to the original ARPA(DARPA?) grant they wanted the Mach microkernel with a BSD interface to prove the viability of the concept of Mach.

iohead 3y ago

No, not quite. The macOS/iOS kernel is extremely Frankenstein-y (not meant in a derogatory way), with the majority of codebase being extremely Apple-specific, and bits and pieces originally taken from Mach and BSD. In particular, there is no microkernel, and there never was. Mach itself was never used as a true microkernel in a commercial setting, with the first such implementation--Mach 3--showing significant real-life performance problems. As such, there is no "BSD on top of a Mach microkernel". It is and has always been a fully monolithic kernel with some subsystems originally derived from Mach (Open Group's Mk 7.3), some from BSD (FreeBSD 5), and the rest developed in-house over the years. Even the layerings aren't always clean, with "on top of" often morphing into "alongside" or "intertwined with".

detourdog 3y ago
What is interesting about Mach to me. Is that now 40 years later it's returning too it's roots of hosting multiple OS's on a single hardware architecture. Apple being able to design to M series chips to match Mach's paper over Mach's deficiencies and leverage it's strength I find very exciting. Originally it was meant to be the foundation computing layer for a campus full of devices.

detourdog 3y ago

The BSD choice dates back to the original ARPA(DARPA?) grant they wanted the Mach microkernel with a BSD interface to prove the viability of the concept of Mach.