ATI’s Senior VP has confirmed that their next generation of PC graphics products will feature much of the technology developed for "Xenos", ATI’s XBOX 360 graphics chip.
Xenos utilises a unified shader architecture at the hardware level, with both Pixel Shaders and Vertex shaders utilising the same ALU resources it becomes a ripe time to implement it with DirectX10 unifying the vertex and pixel shader programming capabilities in the API.
Vertex and pixel processing have previously always been separate hardware functions, though vertex processing moved from a software based solution to hardware with the introduction of NVIDIA’s GeForce 256 and has subsequently got closer to the pixel processing capability with each revision of DirectX Shader Model, to the point where DirextX10 will should dictate the same programming capabilities across both.
Xenos’s design has attempted to remove the texture latency issues from shader programmes by creating a highly threaded design that separates texture instructions from ALU instructions, allowing multiple shader batches to run concurrently, and so it comes as no surprise that ATI should adopt this architecture for the PC, seeing as the investment has already been made.
ATI Xenos Graphics Processor
History of 'Xenos' :
A name that has long since been mentioned in relation to the graphics behind Xenon (the development name for XBOX 360) is R500. Although this name has appeared from various sources, the actual development name ATI uses for Xenon's graphics is "C1", whilst the more "PR friendly" codename that has surfaced is "Xenos".
Xenos is a custom design specifically built to address the needs and unique characteristics of the game console. ATI had a clean slate with which to design on and no specified API to target. These factors have led to the Unified Shader design, something which ATI have prototyped and tested prior to its eventual implementation (with the rumoured R400 development?), with capabilities that don't fall within any corresponding API specification. Whilst ostensibly Xenos has been hailed as a Shader Model 3.0 part, its capabilities don't fall directly inline with it and exceed it in some areas giving this more than a whiff of WGF2.0 (Windows Graphics Foundation 2.0 - the new name for DirectX Next / DirectX 10) about it.
The Xenos graphics processor is not a single element, but actually consists of two distinct elements: the graphics core (shader core) and the eDRAM module. The shader core is a 90nm chip manufactured by TSMC and is currently slated to run at 500MHz, whilst the eDRAM module is another 90nm chip, manufactured by NEC and runs at 500MHz as well. These two chips both exist side by side, together on a single package, ensuring a fast interlink between the two. The main graphics chip, the parent core, could be considered as a "shader core" as this is one of its primary tasks. The eDRAM module is a separate, daughter chip which contains the elements for reading and writing color, z and stencil and performing all of the alpha blending and z and stencil ops, including the FSAA logic.
One element that has been reported on is the number of 150M transistors in relation to the graphics processing elements of Xenon, however according to ATI this is not correct as the shader core itself is comprised from in the order of 232M transistors. It may be that the 150M transistor figure pertains only to the eDRAM module as with 10MB of DRAM, requiring one transistor per bit, 80M transistors will be dedicated to just the memory; when we add the memory control logic, Render Output Controllers (ROP's) and FSAA logic on top of that it may be conceivable to see an extra 70M transistors of logic in the eDRAM module.
Specs of Xbox 360 GPU :
Xenos utilises a unified shader architecture at the hardware level, with both Pixel Shaders and Vertex shaders utilising the same ALU resources it becomes a ripe time to implement it with DirectX10 unifying the vertex and pixel shader programming capabilities in the API.
Vertex and pixel processing have previously always been separate hardware functions, though vertex processing moved from a software based solution to hardware with the introduction of NVIDIA’s GeForce 256 and has subsequently got closer to the pixel processing capability with each revision of DirectX Shader Model, to the point where DirextX10 will should dictate the same programming capabilities across both.
Xenos’s design has attempted to remove the texture latency issues from shader programmes by creating a highly threaded design that separates texture instructions from ALU instructions, allowing multiple shader batches to run concurrently, and so it comes as no surprise that ATI should adopt this architecture for the PC, seeing as the investment has already been made.
ATI Xenos Graphics Processor
History of 'Xenos' :
A name that has long since been mentioned in relation to the graphics behind Xenon (the development name for XBOX 360) is R500. Although this name has appeared from various sources, the actual development name ATI uses for Xenon's graphics is "C1", whilst the more "PR friendly" codename that has surfaced is "Xenos".
Xenos is a custom design specifically built to address the needs and unique characteristics of the game console. ATI had a clean slate with which to design on and no specified API to target. These factors have led to the Unified Shader design, something which ATI have prototyped and tested prior to its eventual implementation (with the rumoured R400 development?), with capabilities that don't fall within any corresponding API specification. Whilst ostensibly Xenos has been hailed as a Shader Model 3.0 part, its capabilities don't fall directly inline with it and exceed it in some areas giving this more than a whiff of WGF2.0 (Windows Graphics Foundation 2.0 - the new name for DirectX Next / DirectX 10) about it.
The Xenos graphics processor is not a single element, but actually consists of two distinct elements: the graphics core (shader core) and the eDRAM module. The shader core is a 90nm chip manufactured by TSMC and is currently slated to run at 500MHz, whilst the eDRAM module is another 90nm chip, manufactured by NEC and runs at 500MHz as well. These two chips both exist side by side, together on a single package, ensuring a fast interlink between the two. The main graphics chip, the parent core, could be considered as a "shader core" as this is one of its primary tasks. The eDRAM module is a separate, daughter chip which contains the elements for reading and writing color, z and stencil and performing all of the alpha blending and z and stencil ops, including the FSAA logic.
One element that has been reported on is the number of 150M transistors in relation to the graphics processing elements of Xenon, however according to ATI this is not correct as the shader core itself is comprised from in the order of 232M transistors. It may be that the 150M transistor figure pertains only to the eDRAM module as with 10MB of DRAM, requiring one transistor per bit, 80M transistors will be dedicated to just the memory; when we add the memory control logic, Render Output Controllers (ROP's) and FSAA logic on top of that it may be conceivable to see an extra 70M transistors of logic in the eDRAM module.
Specs of Xbox 360 GPU :
- 500MHz Custom ATI Graphics Processor
- Unified Shader Core
- 48 ALU’s for Vertex or Pixel Shader processing
- 16 Filtered & 16 Unfiltered Texture samples per clock
- 10MB eDRAM Framebuffer