Thanks for your feedback on this everyone, it really makes me feel that it was worth writing. As you can see, I've updated the article. See section 6.

Although, maybe I should have said this earlier, but there are many things that are simplified about Xbox that reduces it's difficulty to emulate. Things like the fact that all MMIO devices and ram are located on the same 4GB memory address space. For instance, if your executing an instruction in the top of ROM (0xFF000000 - 0xFFFFFFFF) and if that instruction doesn't directly change the EIP register, then it will roll over to 0x00000000 (which is the beginning of RAM) without generating an exception which makes my life a little easier. Also, the PCI bus layout is much more simplified and more definete than a PC's, making it easier to emulate. All of this Xbox hardware stuff is a real adventure

Thanks for explaining.