Linked by Thom Holwerda on Thu 26th Jun 2008 21:52 UTC, submitted by Taylor
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Darwin has another kernel, xnu, which is quite different. MacOS X isn't FreeBSD + stuff, it's Darwin + stuff, and my guess is that even though they use some stuff from FreeBSD it's not really something that would give such a speed-up.
My guess is that the speed comes from the jump to 64-bit (more registers etc) and optimizations. Which is great news indeed. What I do wonder is if they are using some cool SSE(1-4) voodoo as well:) Nice not having to focus on old CPUs 
If you want to know about how OS X is really constructed, there is a an *awesome* video recording from the 24C3 hacker meeting. You can find it under:
http://chaosradio.ccc.de/24c3_m4v_2303.html
IIRC XNU even stands for Xnu is Not Unix.
"I wonder if they simply imported a lot of the changes from freebsd 7, or if that is even possible now with their darwin kernel?
Most of OSX's FreeBSD bits are userland, not kernel. "
well yes but code from freebsd still is an important part of the kernel. if i remember correctly, originally a big part of the freebsd kernel was bolted on top of mach and combined with the driver subsystem io-kit. that's why the bad multithreading support of bsd affected xnu too. most programms don't call mach directly but through bsd-threads.
but i have no idea how much room for improvement is left and if the improvements of freebsd 7 are of any use for xnu. if they happened in a part of the kernel covered by mach, they aren't. but i think that the bsd-part also provided the posix threading model and that has been improved in freebsd 7. apple syncronised the bsd-part of xnu with freebsd 5 in darwin 7 (osx 10.3).
ps:
Here's an interesting statistic, the /bsd folder of the XNU kernel tar ball accounts for 49.2% of the untarred size on disk.
http://www.osnews.com/thread?283223
pss: http://www.kernelthread.com/mac/osx/arch_xnu.html
Edited 2008-06-27 16:34 UTC





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2006-02-22
I wonder if they simply imported a lot of the changes from freebsd 7, or if that is even possible now with their darwin kernel?