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Pixel filling power
Fill rate is becoming less relevant as programmable shading takes hold, but it's still one of the primary measures of overall GPU performance. It's also rather easy to calculate and compare the theoretical peak capabilities for the various cards out there. Here's a look at how the GeForce 7800 GTX fits in.

  Core clock
(MHz)
Pixels/
clock
Peak fill rate
(Mpixels/s)
Textures/
clock
Peak fill rate
(Mtexels/s)
Memory
clock (MHz)
Memory bus
width (bits)
Peak memory
bandwidth (GB/s)
GeForce 6800 32512390012390070025622.4
GeForce 6600 GT AGP500420008400090012814.4
GeForce 6600 GT5004200084000100012816.0
Radeon X80040012480012480070025622.4
GeForce 6800 GT350165600165600100025632.0
Radeon X800 Pro47512570012570090025628.8
Radeon X800 XL 256MB40016640016640098025631.4
Radeon X800 XL 512MB40016640016640098025631.4
GeForce 6800 Ultra425166800166800110025635.2
Radeon X800 XT500168000168000100025632.0
Radeon X800 XT Platinum Edition520168320168320112025635.8
Radeon X850 XT520168320168320112025635.8
Radeon X850 XT Platinum Edition540168640168640118025637.8
GeForce 7800 GTX4301668802410320120025638.4

The GTX is the baddest card on the planet in terms of textured fill rate and memory bandwidth. Even the Radeon X850 XT Platinum Edition, with its crazy-high clock speed, can't match it.

Those are the theoretical peak numbers. With SLI, of course, the theoretical peaks nearly double, if all of the stars are aligned properly. Fortunately, we have several synthetic benchmarks that will measure fill rate for us.

This D3D RightMark batch can demonstrate how the chips perform when applying multiple textures to a pixel. The 7800 GTX comes out looking OK, but the Radeon X850 XT Platinum Edition is sometimes faster. With SLI, of course, it's no contest. I have to admit, though, that I am a little bit perplexed by the zig-zag pattern for the 7800 GTX with three or more textures; it seems to be faster when applying an odd number of textures and slower with an even number.

3DMark05's fill rate tests show the 7800 GTX and its competitors reaching nearly their theoretical peaks when doing multitexturing. In fact, the 7800 GTX is freakishly efficient here, as is the Radeon X850 XT PE. When SLI comes into the picture, the GTX pulls out to an epic lead.