You could have expected something like that from the first SM3.0/HDR graphics test: the 48 pixel processors of the Radeon X1900 XT help it break away from the GeForce 7800 GTX 512 which has half the number of pixel processors and clocks them at a considerably lower frequency, too. Meanwhile, the ASUS EAX1800XT TOP is 20% faster than the standard Radeon X1800 XT and is thus capable of competing with the Nvidia card even though the shaders in this test contain numerous texture lookups.

The “eye candy” mode is interesting because the gap between the Radeon X1900 XT and the ASUS EAX1800XT TOP is increasing towards higher resolutions, and the faster memory of the latter card cannot do anything about that. The larger Z-buffer of the Radeon X1900 must again be the reason for such results.

The second SM3.0/HDR graphics test is much simpler than the first one and doesn’t require the graphics cards to do a lot of math1, so the Radeon X1900 XT cannot beat the GeForce 7800 GTX 512 as effectively as it did in the first test.

The test focuses on HDR effects and realistic dynamic shadows. The Radeon X1900 XT has a considerable advantage over the ASUS EAX1800 XT TOP – we mean the Fetch4 feature which helps taking four samples from single-component textures; and shadows maps are single-component textures. Despite its high operating frequencies of 700MHz GPU and 800 (1600) MHz memory, the ASUS card cannot do any better than the GeForce 7800 GTX.

You can see a curious thing happening when we turn on full-screen antialiasing and anisotropic filtering. The positive effect from the increased frequencies of the ASUS EAX1800XT TOP diminishes as the display resolution grows up, and this graphics card eventually become as fast as the ordinary Radeon X1800 XT. There must be some additional limiting factor; perhaps the card’s Z-buffer is not large enough.

So it is all quite clear in 3DMark06: the ASUS EAX1800XT TOP is not much slower than the Radeon X1900 XT in the SM2.0 tests, but in the SM3.0/HDR tests that use numerous and more complex shaders the gap between these two graphics cards is bigger. Do not forget that the Radeon X1900 XT is more efficient at processing shadows created by means of shadow maps than the ASUS card which is based on the R520 GPU that doesn’t support the Fetch4 feature.