PPC ver of freeBSD ? isent that the main body of os X

Charles Swiger cswiger at mac.com
Wed Feb 4 13:04:05 PST 2004

On Feb 4, 2004, at 3:05 PM, Lucas Holt wrote:
>> MacOS X is using a monolithic kernel which derives from between the 
>> CMU Mach project v2.0 and v2.5 circa 1990, which was Avie Tenavian's 
>> grad project at CMU.  Apple is not using the Mach 3.0 microkernel, 
>> nor is it using "half of the FreeBSD 5 kernel".
> Incorrect!   The original OS X code base does come from next but apple 
> has upgraded the code in 10.3 to use FreeBSD 5.0 code.  
> apple.com/macosx even mentioned that when panther was released.  
> Another document on apple's site i'm looking for again specified that 
> the latest 10.3 kernel was in fact using only the messaging and memory 
> architecture of Mach and the rest was in fact FreeBSD 5.0 code!
> http://developer.apple.com/darwin/history.html

This page isn't wrong, and I believe that the OS X kernel does include 
some FreeBSD 5 code, just as OS X's userland includes some FreeBSD and 
some NetBSD-derived programs.  However, let's consider some real data:

8-base# ident /bin/* /sbin/* /usr/bin/* /usr/sbin/* 2> /dev/null | 
fgrep '$FreeBSD:' | wc -l
9-base# ident /bin/* /sbin/* /usr/bin/* /usr/sbin/* 2> /dev/null | 
fgrep '$NetBSD:' | wc -l
10-base# ident /bin/* /sbin/* /usr/bin/* /usr/sbin/* 2> /dev/null | 
fgrep '$Id:' | wc -l
11-base# uname -a
Darwin base.codefab.com 6.8 Darwin Kernel Version 6.8: Wed Sep 10 
15:20:55 PDT 2003; root:xnu/xnu-344.49.obj~2/RELEASE_PPC  Power 
Macintosh powerpc

1-tanya# ident /bin/* /sbin/* /usr/bin/* /usr/sbin/* 2> /dev/null | 
fgrep '$FreeBSD:' | wc -l
2-tanya# ident /bin/* /sbin/* /usr/bin/* /usr/sbin/* 2> /dev/null | 
fgrep '$NetBSD:' | wc -l
3-tanya# ident /bin/* /sbin/* /usr/bin/* /usr/sbin/* 2> /dev/null | 
fgrep '$Id:' | wc -l
4-tanya# uname -a
Darwin tanya 7.2.0 Darwin Kernel Version 7.2.0: Thu Dec 11 16:20:23 PST 
2003; root:xnu/xnu-517.3.7.obj~1/RELEASE_PPC  Power Macintosh powerpc

So much for userland; shall we consider the kernel, as well?

First, CMU largely stopped work on Mach by the end of 1993 and the Mach 
3 microkernel was largely developed by U/Utah and the OSF, some of 
which became Flex and Flux, if memory serves.  Neither FreeBSD nor 
Apple uses a microkernel, largely because the performance hit for 
context switching between kernel and userspace all of the time is so 
extreme for a true microkernel architecture.

While neither of the two kernels is monolithic, and they support 
dynamic loading of kernel extensions, device drivers reside in kernel 
space, networking is in kernel space, filesystem management (the 
vnode/VFS abstraction) is in kernel space.  A true microkernel would 
have those in userspace and would have nothing beyond a scheduler, VM, 
and basic thread/task management.

Apple did incorporate KAME's IPv6 code, IPFW, and the sysctl MIB 
infrastructure from BSD, and they are offering various POSIX API's like 
pthreads, but POSIX threads itself largely derives from Mach's thread 
model and the Cthreads interface dating back to NEXTSTEP 2.x or 

Apple's IOKit depends on Mach and CoreFoundation, and uses Mach 
primitives and abstractions which are quite distinct from BSD-style 
device drivers.  Take a look at the xnu sources, or how kernel 
extensions and device drivers are implemented under 


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