GeForce 8 Series Architecture


NVidia has just released their new GeForce 8 series, formerly known by its codename, G80. This new series uses a completely different architecture from all other graphic chips, using a unified shader engine. In this article we will explain in details all that is new on this new graphics chip series.

GeForce 8 is the first series to support the forthcoming DirectX 10 (Shader 4.0 model). So first let’s talk about what is new in DirectX 10.

One of the new things on DirectX 10 is geometry processing. Until now the system CPU was in charge of this task. On DirectX 10 geometry processing can now be done by the graphics chip. Geometry processing smoothes curved surfaces and you can see a better quality on character animation, facial expressions and hair.

DirectX 10 provides more resources to the GPU, improving 3D performance. The key differences in GPU resources between DirectX 9 and DirectX 10 you can see in the table below.

Resources DirectX 9 DirectX 10
Temporary Registers 32 4,096
Constant Registers 256 16 x 4,096
Textures 16 128
Render Targets 4 8
Maximum Texture Size 4,048 x 4,048 8,096 x 8,096

In the table below you see a comparison between shader models 1.0 (DirectX 8.1), 2.0 (DirectX 9.0), 3.0 (DirectX 9.0c) and 4.0 (DirectX 10).

  Shader 1.x Shader 2.0 Shader 3.0 Shader 4.0
Vertex Instructions 128 256 512 65,536 *
Pixel Instructions 4+8 32+64 512 65,536 *
Vertex Constants 96 256 256 16 x 4,096 *
Pixel Constants  8 32 224 16 x 4,096 *
Vertex Temps 16 16 16 4,096 *
Pixel Temps 2 12 32 4,096 *
Vertex Inputs 16 16 16 16
Pixel Inputs 4+2 8+2 10 32
Render Targets 1 4 4 8
Vertex Textures 4 128 *
Pixel Textures 8 16 16 128 *
2D Texture Size 2,048 x 2,048 8,192 x 8,192
Int Ops Yes
Load Ops Yes
Derivatives Yes Yes
Vertex Flow Control Static Static/Dynamic Dynamic *
Pixel Flow Control Static/Dynamic Dynamic *

* As DirectX 10 implements unfied architecture as we will discuss in the next page, this number is the total for the whole unified architecture and not for this individual spec.

Besides the increase in resources capacity, there are several new features on DirectX 10, but in summary the goal of this new programming model is to reduce the system CPU role on 3D graphics performance – i.e., it tries to avoid the use of the system CPU as much as possible.

Of course we will have to wait until DirectX 10 games are released to see these new features in action. Some of the games that will be released based on DirectX 10 include Crysis and Hellgate London.

But the main difference between GeForce 8 series and all other graphic chips available today is its unified shader engine, another feature introduced by Shader 4.0 programming model. Let’s talk more about it.

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Author: Gabriel Torres

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.

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