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Mac OS X uses Mach, I have not heard anything about it not being a "proper" microkernel: http://en.wikipedia.org/wiki/MicrokernelVogateer wrote:This is interesting to me, because the idea of a microkernel is very compelling. I would like to see a proper microkernel in action. People might point to OS X as using a microkernel, but my understanding is that OS X doesn't use a proper microkernel.
The emphasis on the last sentence is mine alone.Why is Apple Still Using the Mach Kernel After Mach failed?
The Mach kernel didn't fail; it was the Mach microkernel project that failed. Neither NeXT nor Apple ever used Mach as a microkernel.
Recall that at the time of NeXT's decision to use Mach in NeXTSTEP, Mach wasn't being developed as a microkernel with an external, operating system in userland. Rather, Mach 2.5 simply injected some new ideas on how a microkernel might work into an existing, fat kernel space.
Mach 2.5 was a fat kernel, not the problematic microkernel with horrific performance problems that Mach 3.0 turned out to be.
All the ideological criticisms lobbed back and forth between Linux creator (and fat kernel advocate) Linus Torvalds and Andrew Tanenbaum (the creator of the Minix microkernel) have nearly nothing at all to do with Mach as it is used in Mac OS X.
More Nails in the Coffin
Once again, just for good measure: Mac OS X is not based on a microkernel architecture, and has never used Mach as a microkernel. Apple's XNU kernel is larger than many monolithic kernels, and does not suffer from the intractable performance failure the world associates with Mach microkernel research.
Apple has incorporated progress the Mach project made in development of Mach 3.0, but nothing changed: Mac OS X still does not have a microkernel architecture. Its XNU kernel is not implemented as a microkernel. Apple does not use Mach as a microkernel.
XNU incorporates many technologies from Mach which makes it different than traditional fat kernels such as BSD or Linux. The microkernel myth confuses the facts by associating [anything related to Mach] with [the failure of the Mach microkernel project], which sought to remove BSD from Mach. Since Mac OS X's version of Mach is full of BSD, this false association is rooted in either ignorance or FUD (or both), depending on who is reweaving the myth.
So there you have it: the Mac OS X Microkernel Myth falls apart on the simple discovery that Mac OS X has no microkernel.