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Pixel fill and texturing performance

Peak pixel
fill rate
(Gpixels/s)
Peak bilinear
integer texel
filtering rate
(Gtexels/s)
Peak bilinear
FP16  texel
filtering rate
(Gtexels/s)
Peak
memory
bandwidth
(GB/s)
GeForce GTX 460 1GB 810MHz 25.9 47.6 47.6 124.8
GeForce GTX 470 GC 25.0 35.0 17.5 133.9
GeForce GTX 480 33.6 42.0 21.0 177.4
GeForce GTX 580 37.1 49.4 49.4 192.0
Radeon HD 5870 27.2 68.0 34.0 153.6
Radeon HD 6870 28.8 50.4 25.2 134.4
Radeon HD 5970 46.4 116.0 58.0 256.0

We've already looked at some of the theoretical peak numbers above, but we've reiterated them here a little more fully. These figures aren't destiny for a video card. Different GPU architectures will deliver on their potential in different ways, with various levels of efficiency. However, these numbers do matter, especially among chips with similar architectural DNA.

You'd think 3DMark's color fill rate test would track with the first column of scores above, but it turns out delivered performance is more directly affected by memory bandwidth. That's why, for instance, the Radeon HD 6870 trails the 5870 here, in spite of a higher ROP rate. The GTX 580 is the fastest single-GPU solution, though it can't keep up with the similarly priced multi-GPU options.

We've shunned 3DMark's texture fill test recently because it doesn't involve any sort of texture filtering. That's tragic and sad, since texture filtering rates are almost certainly more important than sampling rates in the grand scheme of things. Still, this is a decent test of FP16 texture sampling rates, so we'll use it to consider that aspect of GPU performance. Texture storage is, after all, essentially the way GPUs access memory, and unfiltered access speeds will matter to routines that store data and retrieve it without filtering.

AMD's samplers are very fast indeed, as the Radeon HD 6870 keeps pace with Nvidia's biggest, baddest GPU. The Radeon HD 5970 is more than twice as fast in this specific case.

Here's a more proper test of texture filtering, although it's focused entirely on integer texture formats, not FP16. Texture formats like these are still widely used in games.

AMD's texture filtering hardware is generally quite a bit faster than Nvidia's with integer formats. The deficit narrows as we move to higher quality filtering levels, but the year-old Radeon HD 5870 remains faster than the GeForce GTX 580.

Happily, after struggling in the dark for a while, we finally have a proper test of FP16 filtering rates, courtesy of the guys at Beyond3D. Nvidia says the GF104 and GF110 can filter FP16 textures are their full rates rather than half. What kind of performance can they really achieve?

The GTX 580 comes pretty darned close to its theoretical peak rate, and it's nearly twice the speed of the Radeon HD 5870. That quite the reversal. The GeForce GTX 460 moves up the chart, too, but doesn't come anywhere near as close as the GTX 580 to reaching its peak potential. The GTX 580's additional memory bandwidth and larger L2 cache—50% better on both fronts—likely account for the difference in delivered performance.