Xenos

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For other uses, see Xenos (disambiguation).

Xbox 360 GPU; note the smaller eDRAM die to the left of the main Xenos die

The Xenos GPU is a custom chip designed by ATI, used in the Xbox 360.

[edit] Overview

Developed under the name "C1", sometimes "R500".^[1] The chip contains two separate silicon dies: the parent GPU and the daughter eDRAM.

• 337 million transistors total (232 million parent shader die+105 million EDRAM daughter die)
• 500 MHz parent GPU (90 nm TSMC process, 232 million transistors)
• 500 MHz 10 MB daughter Embedded DRAM framebuffer (90 nm process, 105 million transistors)
  • NEC designed eDRAM die includes additional logic for color, alpha blending, Z/stencil buffering, and anti-aliasing.
  • 105 million transistors ^[2]
  • 8 render output units
• 48-way parallel floating-point dynamically-scheduled shader pipelines^[3]
  • Unified shader architecture (each pipeline is capable of running either pixel or vertex shaders)
  • Support for a superset of DirectX 9.0 and Shader Model 3.0
  • MEMEXPORT shader function
  • 2 shader ALU operations per pipeline per cycle (1 vec4 and 1 scalar, co-issued)
  • 160 programmable shader operations per cycle (48 ALUs x 2 ops + 16 texture fetch + 32 control flow + 16 vertex fetch)^[4]
  • 48 billion shader operations per second (96 billion shader operations per second theoretical maximum) ^[3]
  • 240 GFLOPS programmable^[4]
• 16 filtered and 16 unfiltered texture samples per clock
• Maximum polygon performance: 500 million triangles per second
• Texel fillrate: 8 gigatexel per second fillrate (16 textures x 500 MHz)
• Pixel fillrate: 16 gigasamples per second fillrate using 4X multisample anti aliasing (MSAA), or 32 gigasamples using Z-only operation; 4 gigapixels per second without MSAA (8 ROPs x 500 MHz)^[1]
• Dot product operations: 24 billion per second or 33.6 billion per second theoretical maximum when summed with CPU operations
• Cooling: Both the GPU and CPU of the console have heatsinks. The CPU's heatsink uses heatpipe technology, to efficiently conduct heat from the CPU to the fins of the heatsink.^[5] The heatsinks are actively cooled by a pair of 60 mm exhaust fans that push the air out of the case (negative case pressure).

[edit] References