Shader performance
We can get a sense of the effectiveness of the G80's unified shader architecture using a battery of vertex and pixel processing tests. These first two are simple vertex processing tests from 3DMark.

The G80 doesn't look like anything special in the simple vertex test, but when we add more complexity, it begins to look more competent.

Next up is a simple particle physics simulation that runs entirely on the GPU. This test uses vertex texture fetch, one of the few Shader Model 3.0 capabilities that the R580 lacks. As a result, it doesn't run on the Radeon X1950 XTX.

Here we begin to get a sense of this unified architecture's potential. The G80 is many times faster than the GeForce 7900 GTX in this task, as we might expect from a GPU designed for broadly parallel vertex processing and quick feedback of SP results into new threads.

Now, let's look at pixel shader performance. Up first is 3DMark's lone pixel shader test.

The G71 and R580+ are very evenly matched here, but the G80 is in a class by itself.

ShaderMark gives us a broader range of pixel shaders to test. Below are the results from the individual shaders, followed by an average of those results.

The G80's pixel shading prowess is remarkable. Overall, its ShaderMark performance is just shy of twice that of the R580+ and G71. These are simple DirectX 9 shaders that don't gain from any of DirectX 10's advances in shader programming, either. The only place where the G80 falls behind the two previous-gen chips is in the three HDR shaders. For whatever reason, it doesn't do as well in those tests.

We can also attempt to quantify the image quality of the G80's pixel shader output by using another feature of ShaderMark. This isn't exactly a quantitative measure of something as subjective as image quality, but it does measure how closely the GPU's output matches that of Microsoft's DirectX reference rasterizer, a software renderer that acts as a standard for DirectX graphics chips.

The G80's image output more closely matches that of the Microsoft reference rasterizer than the images from the other GPUs. This isn't by itself an earth-shattering result, but it is a good indication.