Inside the Xbox Part 1: Procedural Synthesis and Dynamic Worlds
Inside the Xbox Part 2: The Xenon CPU
Don't let all the jargon scare you away, its a neat article.
I'll post links to the other parts (as soon as they are up) as edits in this post itself.
Though there haven't been any updates on the Xbox series, I found Part 1 and Part 2 of a similar series on the cell processor that the PS3 uses.
Part 1: Introducing the Cell Processor: The SIMD Processing Units
Part 2: The Cell Architecture