Pixel Shaders and Physics

Marko Dolenc’s Fillrate Tester doesn’t support even Shader Model 3.0, but suits very well for analyzing graphics architecture performance with older shader code versions. The results obtained in this benchmark may be pretty valuable for those who still play old games. Besides, they give a more or less good idea of the GPU potential.

In fact, all above mentioned shaders test the RBE performance, which is no issue for G200. However, the GPU performance drops dramatically on more complex shaders and gives in completely during per-pixel lighting emulation. Moreover, Nvidia GeForce GTX 280 solution loses even to ATI Radeon HD 4850. The card priced at $499+ yields to a budget solution going for only $199 – what a disaster!

Shader Particles test from 3DMark06 suite is not a fully-fledged graphics test as it emulates a physical model of massive particle systems’ behavior. Collision calculations are performed using pixel shaders and the result is displayed on the screen using vertex shader texture samples. Nevertheless, this test can measure the mathematical GPU performance just fine.

Here the new Nvidia graphics card family seems to be a little better off. However, only lower GPU frequency by ATI Radeon HD 4850 saves the new Nvidia solution from fiasco. However, ATI Radeon HD 4870 seems to be much harder to beat, although Nvidia GeForce GTX 280 almost manages to do it in 1920x1200. This is more than modest performance for a $499+ graphics card with 180W power consumption.

Looks like similar test from 3DMark Vantage suite employs only 1/5 of ATI Radeon 4800’s computational capacity. As a result, Nvidia G200 manages to take the lead. Although this victory is not the success of G200. To be more exact, its only advantage is the fact that scalar architecture from Nvidia doesn’t depend as much on software optimizations as super-scalar architecture from ATI.

Perlin Noise test from 3DMark06 suite estimates the GPU performance in the most complex Shader Model 3.0. It generates a texture using 48 texture samples and 447 mathematics instructions:

As we have expected, TI Radeon HD 4800 is beyond competition here, while Nvidia GeForce GTX 200 performs very modestly. The top model from the new family again lost to the younger fellow from the rivalry camp, although the gap between them is not that big at all.

Increasing the number of texturing units or RBE units will not help to make up for the lower computational capacity. Unfortunately, it is too late and they no longer can fix the power misbalance in the new G200. We can only hope that the new solution will not be so hopeless in real games.

3DMark Vantage POM test displaying the complex landscape with parallax occlusion mapping method again gives the lead to Nvidia GeForce GTX 200.

Although ATI Radeon HD 4850/4870 outperform GeForce 9800 GTX, Only the top model of the two can actually catch up with GeForce GTX 260. We don’t know why, however these could be either software optimizations, or hardware issues. In either case it is very sad outcome for ATI Radeon HD 4000.

Shader Math test is a slightly more complex version of Perlin Noise from 3DMark06.

Here Nvidia GeForce GTX 200 solutions manage to win a formal victory, which indicates that both newcomers boast pretty good mathematical performance. However, the top model, Nvidia GeForce GTX 280, is barely ahead of ATI Radeon HD 4870, while the younger Nvidia GeForce GTX 260 model yields about the same little bit to ATI Radeon HD 4850. So, despite greater complexity of the new Nvidia GeForce GTX 200 cards, they are not always far ahead of the simpler designed ATI Radeon HD 4800.

X-bit Mark test illustrates remarkably well both: mathematical GPU performance and their architectural success. It includes shaders made of mathematical instructions as well as shaders with a lot of texture samples.

This is a complete fiasco for GeForce GTX 200. Nvidia GeForce GTX 280 lost to ATI Radeon HD 4870 in all tests. Moreover, in some of the tests such as Plaid Fabric, 27-Pass Fur and Dynamic Branching – it was a really bad beating. Nvidia GeForce GTX 260 also lost to ATI Radeon HD 4850, though not as badly and even got ahead of the competitor in NPR test (hatch, 8 textures).

So, we managed to reveal the major weakness of the new Nvidia G200: its computational unit working at 1GHz+ frequency doesn’t always bring in the victory. Remember that computational processors are the ones determining the performance in contemporary games that use a lot of shader effects with numerous complex calculations. However, it is indeed very hard to compete with new ATI solutions featuring 800 ALU.

The results are not very optimistic so far: new Nvidia cards didn’t impress us with their mathematical talents, which will inevitably affect the gaming performance in far not the best way. These results are actually pretty strange for solutions aiming at indisputable leadership.