Xenos GPU (Graphics processing unit)

While the first Xbox's graphics processing unit was produced by NVIDIA, the Xbox 360 uses a chip designed by ATI called Xenos. The chip was developed under the name "C1" and "R500" was often used to refer to it. The GPU package contains two separate silicon dies, each on a 90 nm chip with a clock speed of 500 MHz; the GPU proper, manufactured by TSMC and a 10 MB eDRAM daughter-die, manufactured by NEC. Thanks to the daughter die, the Xenos can do 4x FSAA, z-buffering, and alpha blending with no appreciable performance penalty on the GPU. The GPU also houses additional capabilities typically separated into a motherboard chipset in PC systems, effectively replacing the northbridge chip. An aluminum heat sink was implemented to cool the GPU in systems manufactured prior to the second half of 2007; after this time, the GPU heatsink was revised in order to better move heat away from the GPU die. The new heatsink is made from a different material and is connected to a new secondary heatsink (located in front of the CPU heatsink, to the right of the DVD drive) via a copper heatpipe.



Memory and system bandwidth

The console features 512 MB of GDDR3 RAM clocked at 700 megahertz with an effective transmission rate of 1.4 GHz on a 128-bit bus. The memory is shared by the CPU and the GPU via the unified memory architecture. This memory is produced by either Samsung or Qimonda.

The Xbox 360 has an extensive amount of bandwidth in comparison to its competition; however this statistic includes the eDram logic to memory bandwidth, and not internal CPU bandwidths. The eDram internal logic to its internal memory bandwidth is 256 GB/s. The high bandwidth is used primarily for z-buffering, alpha blending, and antialiasing; it saves time and space on the GPU die. Between the eDram die and the GPU, data is transferred at 32 GB/s. The memory interface bus has a bandwidth of 22.40 GB/s and the southbridge a bandwidth of 1 GB/s.

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