Microsoft talked about the newly designed Xbox 360 console at the Hot Chips symposium held this week at Stanford University. The provided details on energy-efficient 45nm CPU with integrated GPU chip that powerd the game machine, compared to the 65nm chip that powered the previous Xbox 360.
Released earlier this summer, the lates 250Gb Xbox 360 is based on the 45nm CPU GPU chip, it has a slimmer chassis, it consumes less power and it is also more quiet than the previous generation console.
Designed by Microsoft and IBM, the integrated CPU GPU SoC offers cost and power savings by eliminating the FSB factor, a single package implementation and IBM's 45nm SOI technology. In addition, the console's design has been simplified. The motherboard's footprint is smaller and single heatsink plus fan design is enough to keep the temperature os the system down.
The Xbox 360 CPU GPU SoC (XCGPU) has 372M transistors. The CPU part has three 3.2GHz PowerPC coreswith 1MB shared L2 cache. The original Xbox 360 CPU was made by IBM and Chartered Semiconductor GLOBALFOUNDRIES is now controlling Chartered and as a result, the new XCGPU is likely to be manufactured by GLOBALFOUNDRIES.
The graphics core includes 48 parallel unified shaders supporting 24 billion shader instructions per second, 4 billion pixels/sec fill rate and 500 million triangles/sec geometry rate. The GPU is also connected through a High Speed IO interface to 10MB EDRAM.
The size of the CPU GPU die is 170 square mm. Compared to the 2005 CPU GPU system, the new chip consumes 60% less power and 50% less Silicon Area.
In order to maintain backward compatibility, FSB (Front Side Bus) and bandwidth had to match the prior FSB, Microsoft said. This was a challenge for Microsoft. Backward compatibility is a combination of both performance and function. Existing verification environments only validate function. The solution came from IBM: sequential equivalence used to validate design migration. The company compared corresponding sequential path outputs from different design representations to ensure their function is the same. In addition, IBM developed a tool for functional equivalence. Pattren based verification was also used to focus on any areas of change. Existing pattern based test were run to validate functions, and new tests were written for any areas of change, including the new FSB logic.