On a purely hardware level, ATI’s Xbox 360 GPU (codenamed Xenos) is quite interesting. The part itself is made up of two physically distinct silicon ICs. One IC is the GPU itself, which houses all the shader hardware and most of the processing power. The second IC (which ATI refers to as the “daughter die”) is a 10MB block of embedded DRAM (eDRAM) combined with the hardware necessary for z and stencil operations, color and alpha processing, and anti aliasing. This daughter die is connected to the GPU proper via a 32MB/sec interconnect. Data sent over this bus will be compressed, so usable bandwidth will be higher than 32MB/sec. In side the daughter die, between the processing hardware and the eDRAM itself, bandwidth is 256MB/sec.
Hardware Discussion: Xbox 360 and Sony PS3
Anandtech has a published an article that goes into some detail comparing the Sony PS3 and the Xbox 360’s hardware specifications including the CPU and GPU.