I've found an interesting article comparing Apple's G5 versus x86 and Mac OS X versus Linux.
Basically resumes to this:
Workstation, yes; Server, no.
The G5 is a gigantic improvement over the previous CPU in the PowerMac, the G4e. The G5 is one of the most superscalar CPUs ever, and has all the characteristics that could give Apple the edge, especially now that the clock speed race between AMD and Intel is over. However, there is still a lot of work to be done.
The server performance of the Apple platform is, however, catastrophic. When we asked Apple for a reaction, they told us that some database vendors, Sybase and Oracle, have found a way around the threading problems. We'll try Sybase later, but frankly, we are very sceptical. The whole "multi-threaded Mach microkernel trapped inside a monolithic FreeBSD cocoon with several threading wrappers and coarse-grained threading access to the kernel", with a "backwards compatibility" millstone around its neck sounds like a bad fusion recipe for performance.
Workstation apps will hardly mind, but the performance of server applications depends greatly on the threading, signalling and locking engine. I am no operating system expert, but with the data that we have today, I think that a PowerPC optimised Linux such as Yellow Dog is a better idea for the Xserve than Mac OS X server.
No more mysteries:
Apple's G5 versus x86, Mac OS X versus Linux
Part One,
Part Two
Blog: "benchmarks" Posts
My name is Nuno Mariz and this is my weblog. I'm a software engineer, living in Porto, Portugal. 
