Although the final specification of the console is thought to be still under discussion at Microsoft - with issues such as the amount of RAM and the whether to include a hard drive still undecided - it's known that Xbox 2 will feature six PowerPC G5 CPU cores and a new model of the ATI Radeon graphics chipset.
As such, the current kits - which, interestingly, are actually branded with the Apple logo - are only similar to final Xbox 2 hardware in the broadest terms. Right now, neither the next-generation ATI part nor the 65nm IBM PowerPC chip - or, for that matter, the three-CPU board needed to hold them - actually exists, so Microsoft is shipping something based on current hardware in order to give developers a running start on the new platform.
The arrival of these prototype kits puts Microsoft well ahead of its rivals in the next-generation console race - since developers have yet to see specifications of Sony's PS3 and Nintendo's N5, never mind actually receiving development hardware.
The news lends weight to recent speculation within the industry that Microsoft will be the first to bring its next console to market, with a launch in autumn 2005 considered likely, while both Sony and Nintendo are thought to be aiming at 2006 launches, with a possibility of Japan-only rollouts in late 2005.