ATi's Radeon 9700 'VPU' - An Introduction
ATi's new high-end 3D chip, also known under its code name "R300," was designed for Microsoft's upcoming DirectX 9 specification. ATi calls it 'VPU' for Visual Processing Unit to distinguish it from the term 'GPU,' which was invented by NVIDIA at the introduction of GeForce256 in 1999. The step from the Direct X 8.1 of today to DX9 will be another major leap forward, as it will allow a new level of 3D quality and add a new amount of 3D features. In Direct X 9, vertex shader programs can be much more complex than before, as the new vertex shader specs add flow control, a lot more constants, as well as up to 1024 vertex shader instructions per program. While the new pixel shaders will still not allow flow control, the maximum number of pixel shader instructions has grown to 160. The real key feature of DirectX 9, however, is the introduction of RGBA values in 64 (16-bit FP per color) as well as 128-bit (32-bit FP per color) floating point precision. This great increase of color precision allows a stunningly new amount of visual effects and picture quality.
DirectX 9 won't be out for several months and so you might wonder about today's value of a 3D chip that has been designed for those future specifications. This is a very valid question, since DirectX 9 titles won't ship before Microsoft has actually released DirectX 9. However, OpenGL titles that are programmed for the above-mentioned features can fully use Radeon 9700 already today. It's another question how long we will have to wait until we will indeed see the first games that take full advantage of the new features, but e.g. Id's upcoming Doom 3 will at least make use of a few of Radeon 9700's new capabilities.
Besides all this new stuff, Radeon 9700 will also have enough brute force to accelerate today's DX7 and DX8 games to beyond what we have seen before. The eight-pixel-pipeline rendering unit, four parallel vertex shaders and a 256-bit memory interface with a bandwidth of 20 GB/s make sure that the previous performance leader is left in the dust. Radeon 9700 might be a bit ahead of its time, but not so far ahead that you wouldn't be able to enjoy it already today.