Pixel-filling power
We'll begin our testing with a quick look at some theoretical numbers for pixel throughput. These numbers are mainly related to the card's ability to push pixels through the traditional graphics pipeline, and they are becoming increasingly less important as programmable shading becomes more prevalent. They are still relevant in many of today's games, though, so we'll have a quick look at them. I've included the Radeon X1300 XT and Radeon X1650 Pro in the table below for reference, even though we don't yet have examples of those cards to test.
| Core clock (MHz) | Pixels/ clock | Peak fill rate (Mpixels/s) | Textures/ clock | Peak fill rate (Mtexels/s) | Effective memory clock (MHz) | Memory bus width (bits) | Peak memory bandwidth (GB/s) | |
| Radeon X1300 XT | 500 | 4 | 2000 | 4 | 2000 | 800 | 128 | 12.8 |
| Radeon X1600 XT | 590 | 4 | 2360 | 4 | 2360 | 1380 | 128 | 22.1 |
| Radeon X1650 Pro | 600 | 4 | 2400 | 4 | 2400 | 1400 | 128 | 22.4 |
| Radeon X1800 GTO | 500 | 12 | 6000 | 12 | 6000 | 1000 | 256 | 32.0 |
| GeForce 7600 GT | 560 | 8 | 4480 | 12 | 6720 | 1400 | 128 | 22.4 |
| GeForce 7800 GT | 400 | 16 | 6400 | 20 | 8000 | 1000 | 256 | 32.0 |
| All-In-Wonder X1900 | 500 | 16 | 8000 | 16 | 8000 | 960 | 256 | 30.7 |
| Radeon X1800 XL | 500 | 16 | 8000 | 16 | 8000 | 1000 | 256 | 32.0 |
| Radeon X1800 XT | 625 | 16 | 10000 | 16 | 10000 | 1500 | 256 | 48.0 |
| Radeon X1900 XT | 625 | 16 | 10000 | 16 | 10000 | 1450 | 256 | 46.4 |
| GeForce 7800 GTX | 430 | 16 | 6880 | 24 | 10320 | 1200 | 256 | 38.4 |
| Radeon X1900 XTX | 650 | 16 | 10400 | 16 | 10400 | 1550 | 256 | 49.6 |
| Radeon X1950 XTX | 650 | 16 | 10400 | 16 | 10400 | 2000 | 256 | 64.0 |
| GeForce 7900 GT | 450 | 16 | 7200 | 24 | 10800 | 1320 | 256 | 42.2 |
| GeForce 7800 GTX 512 | 550 | 16 | 8800 | 24 | 13200 | 1700 | 256 | 54.4 |
| GeForce 7900 GTX | 650 | 16 | 10400 | 24 | 15600 | 1600 | 256 | 51.2 |
| GeForce 7950 GX2 | 2 * 500 | 32 | 16000 | 48 | 24000 | 1200 | 2 * 256 | 76.8 |
The Radeon X1900 XT 256MB has the same basic specs as the 512MB version, save for memory size. That puts it in a very respectable place. The X1950 XTX, meanwhile, has a tremendous memory bandwidth advantage on everything but the "SLI on a stick" dual-GPU GeForce 7950 GX2.
How do these numbers translate into performance on synthetic fill rate benchmarks?
The X1950 XTX's faster RAM helps it make big gains over the Radeon X1900 XTX in the single-textured fill rate test, despite having the same GPU clock frequency. Once we get into multitextured pixels, though, that advantage is muted.
Of course, these numbers aren't destiny in real-world applications. The GeForce cards do especially well here thanks to their ability to use one of the ALUs in each of their pixel shader processors for texturing. The R580-derived cards, meanwhile, have 16 dedicated texture address units and 48 dedicated pixel shader processors at their disposal. In other words, the two architectures allocate their resources quite differently, and the implications are difficult to predict with a simple fill rate test.
