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Synthetic Tests: Pixel Shaders

Using the same Fillrate Tester we’ll see the NV40 executing pixel shaders of a varying degree of complexity.

These are excellent results, don’t you agree? NVIDIA’s claims about a considerable improvement of the pixel shader speed seem to be true to life.

What’s curious, the GeForce 6800 Ultra enjoys a performance gain from working with the 16-bit precision, which is even bigger than the GeForce FX 5950 Ultra has. When talking about a faster pixel shader execution, NVIDIA didn’t mention the problem of half-precision calculations, and that made us think that the NV40 wouldn’t have any performance gains from reducing the precision. Practice shows, however, that the pixel processor of the NV40, already accelerated in comparison to the NV38, can get an additional boost from switching to the low calculation accuracy.

It’s also curious that the NV40 executed the simple version 1.1 pixel shader slower than the simple version 2.0 shader, unlike the NV38.

The situation remained the same when we disabled Z writes. So we have nothing to add to the above words.

When we disabled color writes, the NV40 only started outputting 32 Z-values per clock cycle with the simple shaders, but had a smaller result with the complex version 2.0 pixel shaders. Well, this behavior is peculiar to all the graphics cards, it is just more conspicuous with the NV40.

Right now we’re working in our test labs on a project of a complex test that would allow evaluating modern DirectX 9-compativle graphics cards. We used Xbitmark in this review to check out the performance of the graphics cards at executing DirectX 9 pixel shaders of varying complexity.

The NV40 has an easy win over the ex-champion RADEON 9800 XT, which is especially clear with the sophisticated “27-Pass Fur” shader. The new chip outperforms the RADEON by 1.5-3 times nearly everywhere! It really sets new standards for PC graphics hardware.

Next go the tests of the pixel shader speed from 3DMark suites:

The performance of the CPU and the system at large limits the speed of the graphics cards in the lowest resolutions in 3DMark2001, but in higher resolutions the NV40 shows higher results than its adversaries. In 1600x1200, the GeForce 6800 Ultra is 2.5 times faster than the GeForce FX 5950 Ultra and 1.5 times faster than the RADEON 9800 XT.

The GeForce 6800 Ultra is good at executing version 1.4 pixel shaders, too, leaving behind the ex-leader RADEON 9800 XT.

The GeForce 6800 Ultra is the best at dealing with version 2.0 pixel shaders and the gap is astonishing. This performance promises excellent results in modern shaders-heavy games.

Now let’s check out vertex processors.

 
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