[bluejekyll]

Apple didn’t end up on a BSD kernel. They started on Mach (from NeXT) and then made it more performant with XNU by not being so pedantic about microkernels.

BSD is just a supported kernel ABI.

Edit: I just found these docs, so I suppose it’s a bit more complicated that I’m stating, I.e. there are portions of the FreeBSD kernel directly in macOS https://developer.apple.com/library/archive/documentation/Da...

[chasil]

I only know what I've read.

"XNU was a hybrid kernel derived from version 2.5 of the Mach kernel developed at Carnegie Mellon University, which incorporated the bulk of the 4.3BSD kernel modified to run atop Mach primitives..."

https://en.m.wikipedia.org/wiki/XNU

[jbverschoor]

4.3BSD is not FreeBSD

[bluejekyll]

This is from the link I provided: “The BSD portion of the OS X kernel is derived primarily from FreeBSD, a version of 4.4BSD that offers advanced networking, performance, security, and compatibility features. BSD variants in general are derived (sometimes indirectly) from 4.4BSD-Lite Release 2 from the Computer Systems Research Group (CSRG) at the University of California at Berkeley.”

[fluidcruft]

After NeXTStep was adopted by Apple, they hired a bunch of the FreeBSD core developers and updated the BSD service and userland using FreeBSD. Apple was actually already messing around with Mach prior to that with MkLinux so there was some initial speculation that they might port to MkLinux rather than update NeXT's Mach+BSD hybrid.

[p_l]

The code updates are very limited, though. To the point that for one's own sanity it's better to assume userland is 4.3BSD unless marked otherwise (been burned by this myself in code that assumed every BSD had changes from ~1994 NetBSD)

[teh_klev]

I think you're replying to the wrong comment.

[p_l]

MacOS X essentially started by updating the NeXT core to latest OSFMK distribution, which was hybrid system (bsd server integrated into kernel space) powering the BSD alternative to SystemV - OSF/1 (most famous of them being DEC OSF/1 aka Digital Unix aka Compaq Tru64). They applied bits of FreeBSD to the bsd server code and over time improved its concurrency, but considerable portion of XNU is code that is called by bsd server but not part of bsd server (IOKit, among other things)