As much as Bill hates to admit it, rather then using the IBM 3.2 GHz chips that the Xbox will 
“We purchased a number of Apple G5’s because very specific hardware components of the G5 allow developers to emulate some of the technology behind future Xbox products and services,” a Microsoft spokesperson said in a statement. “This is an interim development tool that will be replaced with a more powerful and comprehensive solution later.”
At least they bought them instead of asking Apple to loan then a few. :-) My question is which Microsoft department won the battle to take them home with them after the Xbox release party.