[TUHS] Is there a good, even definitive, list of reimplementations of the Unix kernel? What would good cut-off criteria be?

[John R Levine via TUHS]

> OSX uses a microkernel, Mach. Thing is more and more code got moved from user space into the kernel to speed it up. First OSF1 moved more code into kernel space, then NeXT, then Apple. But the kernel definitely started out as the Mach micro kernel.

That's what almost always happens, start with a microkernel, find that all 
the context switches are killing performance so you move all the pieces 
into one place and you end up with yet another macrokernel.

QNX is probably the most successful microkernel system.  It's even POSIX 
compatible.

Regards,
John Levine, johnl at taugh.com, Taughannock Networks, Trumansburg NY
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