Performance in Synthetic Benchmarks

Futuremark 3DMark05

The new card from AMD is successful in 3DMark05, scoring over 18.000 points. It outperforms the GeForce 8800 GTS as well as the more advanced and expensive GeForce 8800 GTX. But you should be aware that 3DMark05 defaults to 1024x768 resolution without full-screen antialiasing and it cannot reveal graphics architecture bottlenecks which are not directly related to performance of the shader subunits.

The fill rate and performance of the rasterization subunits are the theoretical bottlenecks in the Radeon HD 2900 XT architecture, so it makes sense to check out individual 3DMark05 tests at higher resolutions and with 4x FSAA.

We see it right away that the Radeon HD 2900 XT is no match to the G80-based cards in scenes that are sensitive to texturing speed because even the cut-down GeForce 8800 GTS has 24 TMUs with two texture filter units per each and 20 ROPs whereas the new card from AMD is limited to 16 units of each type, although clocked at a higher frequency. As a result, the Radeon HD 2900 XT can only surpass its predecessor, the gap between them being roughly equal to the difference in their core clock rates. The impressive memory bandwidth cannot help the new card, either, as the 1920x1200 results show.

The Radeon HD 2900 XT performs better in the second test. Not surprisingly as this test is not as heavy on the graphics card’s TMUs and ROPs as the first one. The second test needs high vertex shader performance and the new graphical architecture from AMD can deliver it as we made sure in our theoretical tests – it was much faster at processing geometry than the Nvidia GeForce 8800 series. The results may seem not very high from this point of view because the new card cannot reach the level of the GeForce 8800 GTS either due to the features of the test itself (3DMark05 is limited to version 2 shaders) or to some imperfections in the Catalyst driver.

Although limited to Shader Model 2.0, the third test is hungry for computing resources of the GPU as well as for texturing speed. The R600 has got an opportunity to strike back thanks to its 64 superscalar computing modules, each capable of executing 5 operations per clock cycle. The Radeon HD 2900 XT is still somewhat slower than the GeForce 8800 GTS, yet it passes through this test better than through the former two.

So, although winning in the default mode, the AMD Radeon HD 2900 XT cannot compete with the GeForce 8800 GTS, let alone with the GeForce 8800 GTX, in 3DMark05 if FSAA is enabled in popular display resolutions. We should make allowances for the age of this benchmark, though. It doesn’t use such features of modern GPUs as the support of Shader Model 3.0 and HDR lighting with floating-point color representation. 3DMark06 suits newest graphics cards much better.