X-bit labs

S3 GammaChrome S18 Pro Graphics Adapter Review (page 6)

Category: Video

by Alexey Stepin

[ 04/19/2005 | 07:19 PM ]

Pixel Shader Performance

Marco Dolenc’s Fillrate Tester can also check out the speed of the pixel processors. Below are the results we got with enabled color and Z writes:

The performance of the GammaChrome with simple pixel shaders is quite expectedly similar to that of the RADEON X600 PRO. It’s worse with the more complex per-pixel-based lighting where the new GPU is even slower than the RADEON X300.

Take note that the GeForce 6600 works faster in the half-precision mode, but its performance is anyway much better than of the rest of the participants of the test even at 32-bit precision.

When Z writes are disabled, we again see the GammaChrome S18 being slower with version 2.0 pixel shaders than the RADEON X300 with its 325MHz core frequency and the same number of pixel pipelines.

The picture is different in the contrary case – with disabled color writes and enabled Z writes. The diagram is indicative of high efficiency of the GammaChrome processor as it works with the Z buffer, especially when executing simple shaders.

Alas, the performance of the GammaChrome with pixel shaders isn’t as high as we might wish. The GammaChrome is no match to ATI’s solutions, not to mention the GeForce 6600 with its twice as many pixel pipelines, in tests which emphasize the pixel shader speed. The S3 card wins only three tests against the RADEON X600 PRO and six tests against the RADEON X300. The GammaChrome is especially weak at processing mathematics-heavy pixel shaders like Dot Product Bump Mapping + Specular + Reflection or Wood.