X-bit labs

Highly Defined: ATI Radeon HD 2000 Architecture Review (page 19)

Category: Video

by Anton Shilov , Yaroslav Lyssenko, Alexey Stepin

[ 05/15/2007 | 07:34 AM ]

Pixel Shader Performance

The Radeon HD 2900 XT behaves here similarly to its predecessor, however, its performance drops only on pixel shader 2.0 per-pixel lighting. It looks like this particular test hardly measures mathematical performance of the R600, but rather shows that the chip has serious performance bottlenecks inside, e.g., slow texture units, which may negatively affect its speed in real-world applications. Still, the new board is definitely faster than the GeForce 8800 GTS and, in two cases even shows higher performance compared to the model 8800 GTS.

The times when ATI’s hardware used to lead in Xbitmark test have gone: as we see, there are lot of cases when Nvidia’s GeForce 8800 GTX leaves its rival in the dust. Moreover, there a number of cases when the new board does not outperform its predecessor significantly due to one simple reason: the newcomer has a an Achilles heel with its 16 texture mapping units.

As is known, 3DMark05 and 3DMark06 benchmarks use similar pixel shader for appropriate test of the suite, however, the latter still works a little faster.

The GeForce 8800 GTX is an indisputable leader here, whereas the Radeon HD 2900 XT’s performance is nearly similar to that of the GeForce 8800 GTS. We are not sure that this test actually measures computing power of modern GPUs, but have reasons to believe that it compares the speed of texture sampling, memory controllers and/or caches on the first place. Nonetheless, the Radeon HD 2900 XT does not outperform its main rival here despite of the fact that it has higher fillrate than Nvidia’s GeForce 8800 GTS.