A 21.6 GB/s front side bus, aggregated 10.8 GB/s upstream and downstream, connected Xenon with the graphics processor/ northbridge. The original chip used a 90 nm process, although a newer 65 nm process SOI revision was implemented on later models, which was in-turn superseded by a 45 nm combined CPU and GPU chip. However, to reduce CPU die size, complexity, cost, and power demands, the processor used in-order execution in contrast to the Intel Coppermine 128-based Pentium III used in the original Xbox, which used more complex out-of-order execution. Each core of the CPU was capable of simultaneous multithreading and was clocked at 3.2 GHz.
This led to an approximate 50 percent savings in required band-width and memory footprint making the CPU having a theoretical peak performance of 115.2 GFLOPS, being capable of 9.6 billion dot products per second. The VMX128 was also modified by the addition of direct 3D (D3D) compressed data format. The dot-product instruction took far less latency than discrete instructions. The SIMD vector processor (VMX128) was modified for the Xbox to include a dot-product instruction. The CPU emphasized high floating point performance through multiple FPU and SIMD vector processors in each core. The XCPU, named Xenon at Microsoft and "Waternoose" at IBM, is a custom triple-core 64-bit PowerPC-based design by IBM.
The Xbox 360 took a different approach to hardware compared to its predecessor.
0 kommentar(er)
