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NVIDIA GeForce 8800 GTX / GTS (G80) - The World's First DX10 GPU

By Vijay Anand - 9 Nov 2006

NVIDIA's Unified Architecture - Part 1

NVIDIA's Unified Architecture - Part 1

For a unified shader architecture to be fulfilled, there were a few prerequisites to be satisfied as it's not a simple re-organization of shader units. Referring back to the traditional GPU architecture highlighted on the earlier page:-

  • The vertex and shader units of the traditional GPU design had differing feature sets that complied with the earlier Shader Model and DirectX standards. These had to be standardized for the common shader unit, which would assume its multipurpose role in a unified shader architecture. Microsoft's DirectX 10 specification covers that area and we'll detail that later.
  • Secondly, because of the vertex and shader unit's differing abilities on the traditional pipeline coupled with the old pipeline hierarchy where data flows linearly, separate instruction set addressing are used. To better facilitate the move to unified shader architecture, a unified instruction set mandated by Shader Model 4.0 in the DirectX 10 specifications has to be adopted (more on this later).
  • Thirdly, there should be an efficient dispatcher and load balancer governing the populating of the shader processing units in the unified model.

Since NVIDIA's G80 GPU adheres to the DirectX 10 spec, it has got the above-mentioned requirements covered, but here's how they accomplished it. Gone are the conventional and limited fixed function vertex and pixel shader units and these have been replaced with128 unified stream processors. Don't be intimidated by the term stream processor (which can be as easily referred to us a general purpose shader processor). For quite a while, graphics processors have been functioning like stream processors, albeit in a more constricted manner. Since the G80 has bolstered the shader processors to be of equal standing, they have now become general floating-point processors and can now tackle vertices, pixels, geometry, physics and more. Here's how the G80 GPU architecture stands now:-

Completely unlike past GPU designs, the unified massively parallel shader design of the G80 GPU is geared for the next generation operating system, API and games. It will most likely be a while to fully realize its potential, but it has other enhancements to ensure it stays on top (for now at least). The top half corresponds to the NVIDIA Unified Architecture while the bottom half represents the new Lumenex Engine, which we'll touch upon later.

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