Xenos

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

The Xenos GPU is a custom graphics processing unit (GPU) designed by ATI, used in the Xbox 360 video game console. Developed under the codename "C1,"^[1] it is in many ways the precursor to the R600 desktop PC graphics card series. The chip contains two separate silicon dies: the parent GPU and the daughter eDRAM.

Specifications

On chip, the shaders are organized in three SIMD engines with 16 processors per unit, for a total of 48 shaders. Each of these shaders is comprised of two ALUs that can execute a single operation per cycle, so that each shader unit can execute two floating-point operations per cycle.

• 337 million transistors in total
• 500 MHz 10 MiB daughter embedded DRAM (eDRAM) framebuffer on 90 nm process.
  • NEC designed eDRAM die includes additional logic (192 parallel pixel processors) for color, alpha compositing, Z/stencil buffering, and anti-aliasing called “Intelligent Memory” (eDRAM), giving developers 4-sample anti-aliasing at very little performance cost.
  • 105 million transistors ^[2]
  • 8 Render Output units
    • Maximum pixel fillrate: 4 gigapixel per second (8 ROPs x 500 MHz)
    • Maximum Z sample rate: 8 gigasamples per second (2 Z samples x 8 ROPs x 500 MHz), 32 gigasamples per second using 4X anti aliasing (2 Z samples x 8 ROPs x 4X AA x 500 MHz)^[1]
    • Maximum anti-aliasing sample rate: 16 gigasamples per second (4 AA samples x 8 ROPs x 500 MHz)^[1]
• 500 MHz parent GPU on 90 nm TSMC process of total 232 million transistors
  • 48-way parallel floating-point dynamically-scheduled shader pipelines^[3]
    • Unified shader architecture (each pipeline is capable of running either pixel or vertex shaders)
    • 10 FLOPS per pipeline per cycle
    • Maximum vertex count: 1.5 billion vertices per second ( (48 shader pipelines x 500 MHz) / 16)
    • Maximum polygon count: 500 million triangles per second^[3] (1.5 Billion vertices / 3 vertices per tiangle)
    • Maximum shader operations: 48 billion per second (2 ALU x 48 shader pipelines x 500 MHz)
    • 240 GFLOPS (10 FLOPS x 48 shader pipelines x 500 MHz)^[4]
    • MEMEXPORT shader function
  • 16 texture filtering units (TF) and 16 texture Addressing unit (TA)
    • 16 filtered samples per clock
      • Maximum texel fillrate: 8 gigatexel per second (16 textures x 500 MHz)
    • 16 unfiltered texture samples per clock
  • Maximum Dot product operations: 24 billion per second
  • Support for a superset of DirectX 9.0c API DirectX XBOX 360, and Shader Model 3.0
• 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. The heatsinks are actively cooled by a pair of 60 mm exhaust fans.
• In August of 2008, the Xenos is reported to be receiving a die shrink to 65nm. This change will result in less voltage being used and less heat being produced. Source: Source: http://blogs.mercurynews.com/aei/2007/10/xbox_360_secrets_after_falcon_comes_jasper.html

References

See also

• Xbox 360
• ATI Technologies
• Microsoft