X-bit labs

The Fast and Furious: ATI Radeon X1900 XTX Review (page 10)

Category: Video

by Anton Shilov , Alexey Stepin

[ 01/24/2006 | 08:28 PM ]

Theoretical Tests

Pixel Shader Performance

As we see, the Radeon X1900 XTX is only slightly better compared to the Radeon X1800 XT in simple pixel shaders amid massively improved theoretical pixel shader power, which means that the actual performance limiter in cases of simple pixel shaders 1.1, 1.4 and 2.0 is memory bandwidth and caching efficiency, not the lack of computing power. The GeForce 7800 GTX 512 with its lighting speed 1700MHz memory is substantially ahead of both Radeon products in such cases.

Once pixel shaders get complex, the Radeon X1900 XTX leaves the Radeon X1800 XT behind by the factor of 2 and also manages to outstrip the GeForce 7800 GTX 512, but not that significantly.

Obviously, the Radeon X1900 XT demonstrates excellent results in cases where outstanding mathematical power is required and shows magnificent results in scenes that include dynamic branching and a lot of maths.

Since ATI has implemented special branch execution units into its Radeon X1000-series, the new Radeon X1900 XTX leaves no chances to the GeForce 7800 GTX 512 and manages to leave the rival in the dust with 3-4 times performance lead.

We can notice that in the case of shaders that depend on arithmetic performance of the GPU the Radeon X1900 XTX may be two times faster than the predecessor. Nevertheless, given that the shaders originally written for the Radeon X800 and the GeForce 6800-class hardware are so effortless for the Radeon X1900 XTX and the GeForce 7800 GTX 512 that the main factors that limit performance turn out to be texture fetches and cache efficiency/memory bandwidth.

The outcome is that even in synthetic benchmarks that reproduce typical workload, the GeForce 7800 GTX 512 showcases pretty high results, which implies that the product is, in fact, very well-balanced.