What can you tell us about the CPU inside Microsofts XBox 360?
Jon Stokes: The Xenon CPU is a three-core, multithreaded PowerPC processor designed by IBM. Each of the three cores is very similar to the general-purpose CPU in the Cell BE (the PS3’s processor), but it has some additional vector processing resources. Probably the most important thing to note about Xenon is that it handles caching in a very special way that makes it more effective for media-intensive workloads like video decoding and gaming. Streaming media applications tend to “dirty” the cache, which means that instead of storing a single working set in the cache and using that data for a while, they’re constantly moving data /through/ the cache. This kind of behavior makes very poor use of the cache, and in fact streaming data from one thread can result in non-streaming data from another thread being booted out of the cache needlessly. Xenon’s fix for this is to “wire down” certain sections of the cache and dedicate them to a single thread. That way, a thread that is only moving da
