As we reported earlier, IBM processors are indeed the Xbox 2 development platform of choice.
The big news to us is that the XBOX 2 SDK has been seeded to developers on dual Apple Power Mac G5 systems running a custom Windows NT Kernel.
The Apple Power Mac G5 is based upon two of IBM's 64-bit Power PC processors and features ATi RADEON 9800 Pro (R350) graphics. However the R350 is believed to be an interim solution and will, in due course, be superseded by the forthcoming ATI R420.
Interestingly the SDK apparently also features an Apple logo on a side bar within the application.
What we don't yet know is whether the custom Windows NT Kernel for the 64-bit capable IBM Power PC processors is 64-bit or 32-bit.
Though as ATI is so clearly behind with even its iAMD64 device drivers for both Intel and AMD x86-64 platforms, we suspect that it's 32-bit.
Let us know if you know. µ