Darwin/x86 ported to Xbox

What is Darwin?
Darwin is the base of Mac OS X, comprising the kernel "xnu", the system libraries and the UNIX tools.

Can I run Mac OS X on the Xbox?
No. Darwin does not include the Mac OS X GUI, and the future x86 version of Mac OS X will only run on Apple branded hardware. Besides that, at least the current builds of Mac OS X for x86 need SSE2 and SSE3 support of the CPU - the Xbox CPU has neither. And of course, OS X wouldn't run with only 64 MB or RAM, and very slowly with only 128 MB.

Why should I run Darwin instead of Linux?
You should not. The Xbox version of Linux is far more advanced at the moment than the Xbox version of Darwin. If you are interested in Apple's modified-microkernel BSD-UNIX, have a look at it, though.

How to run Darwin
The patches and binaries currently support Darwin 8.0.1 only (this is the base of Mac OS X 10.4.0).
* You need a 128 MB Xbox for this for now!
* Use a PC with at least a Pentium 4 or Athlon 64 CPU (because of SSE2) to install Darwin/x86 8.0.1 on a fresh hard disk (should be at least 2 GB).
* Replace /System/Library/Extensions/IOPCIFamily.kext with the patched version.
* Set up a DHCP and TFTP server to send "bootkernel.elf" to the Xbox's MAC.
* Run cromwell and choose "Etherboot".
"bootkernel.elf" already includes the patched Darwin kernel, so there is no need to replace "/mach_kernel".

http://www.xbox-linux.org/wiki/Darwin