X-bit labs

ATI RADEON X1000: Brand-New Graphics Architecture from ATI Explored (page 21)

Category: Video

by Alexey Stepin , Yaroslav Lyssenko, Anton Shilov

[ 10/05/2005 | 12:05 PM ]

Pixel Shader Performance

The new version of Fillrate Tester includes a lot of shader benchmarks. We selected only the ones with full precision pixel shaders: half-precision is no longer acute nowadays.

RADEON X1800 XT copes with the simple shaders version 1.1-2.0 almost as well as GeForce 7800 GTX. However, once the shader length increases, our hero starts falling far behind the rival. When it comes to the most complex shader of this test, PS 2.0 Per Pixel, GeForce 7800 GTX turns almost twice as fast as RADEON X1800 XT! RADEON X1800 XL finally manages to get ahead of GeForce 6800 Ultra, and to significantly reduce the gap to RADEON X850 XT Platinum Edition, although it cannot outpace the predecessor. Unfortunately, RADEON X1800 cannot boast much here: GeForce 7800 GTX does look better in this test.

Xbitmark results prove this point once again: the overall performance of RADEON X1800 XT is lower or the same as that of GeForce 7800 GTX.

Although there are a few exceptions. One of them occurs during the processing of multi-pass shaders (27-Pass Fur) and shaders using dynamic branching. In both these cases RADEON X1800 XT is undefeated. Moreover, in case of the hardest Heavy Dynamic Branching, it is twice as fasta s the rival.

In other words, Ultra-Threading architecture and potentially bigger number of time registers do provide the performance advantage in those cases where it is theoretically possible: during multi-pass rendering and processing of complex shaders with branching. Looks like Ultra-Threading and intellectual memory controller ensured impressively high results in 27-Pass Fur test. Unfortunately, NPR shader (hatch, 10 textures ps3) refused to run on RADEON X1000, and all Xbitmark displayed at that point was an empty screen.

As we have just found out from the simple pixel shader processing tests, RADEON X1800 can sometimes lose to NVIDIA solutions. However, the shader test version 1.1 included with the 3DMark 2001 SE benchmarking suite shows that RADEON X1800 XT and GeForce 7800 GTX work almost equally fast.