Pixel-filling power
We've already talked about GeForce 8600 GT and GTS specifications, but it's sometimes enlightening to do some basic math to see what those specs are likely to mean for performance. Here's a look at the 8600 series' specifications along with their closest competitors'. Notice that I've included separate entries for the higher-clocked XFX cards. Our review samples are these faster, more expensive models, so keep that in mind as you see our test results.
Also, these numbers are important to determining overall performance, but they are all—including memory bandwidth—growing less important as the use of programmable shading power becomes more extensive.
| 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 X1650 XT | 575 | 8 | 4600 | 8 | 4600 | 1350 | 128 | 21.6 |
| Radeon X1650 Pro | 600 | 4 | 2400 | 4 | 2400 | 1400 | 128 | 22.4 |
| GeForce 7600 GT | 560 | 8 | 4480 | 12 | 6720 | 1400 | 128 | 22.4 |
| GeForce 8600 GT | 540 | 8 | 4320 | 16 | 8640 | 1400 | 128 | 22.4 |
| XFX GeForce 8600 GT 620M | 620 | 8 | 4960 | 16 | 9920 | 1600 | 128 | 25.6 |
| GeForce 8600 GTS | 675 | 8 | 5400 | 16 | 10800 | 2000 | 128 | 32.0 |
| XFX GeForce 8600 GTS 730M | 730 | 8 | 5840 | 16 | 11680 | 2260 | 128 | 36.2 |
| GeForce 7900 GS | 450 | 16 | 7200 | 20 | 9000 | 1320 | 256 | 42.2 |
| Radeon X1950 Pro | 575 | 12 | 6900 | 12 | 6900 | 1380 | 256 | 44.2 |
| XFX GeForce 7900 GS 480M | 480 | 16 | 7680 | 20 | 9600 | 1400 | 256 | 44.8 |
| Radeon X1900 XT | 625 | 16 | 10000 | 16 | 10000 | 1450 | 256 | 46.4 |
The GeForce 8600 GT tucks right into its place next to the Radeon X1650 XT and GeForce 7600 GT without rocking the boat. At stock speeds, it has the same memory bandwidth as the 7600 GT, but it has more texturing capacity than either of its rivals.
The GeForce 8600 GTS, on the other hand, is priced to challenge the Radeon X1950 Pro and GeForce 7900 GS, but both of those cards have about 10GB/s more memory bandwidth than a stock GeForce 8600 GTS, thanks to their 256-bit memory interfaces. The 8600 GTS can more than hang with them on texturing capacity, but we still have a mismatch of sorts in hardware.
How do these numbers play out in a synthetic fill rate test?
The GeForce 8600 series cards tend to underachieve a bit here, with neither reaching its theoretical peak fill rate, even with multitexturing. Then again, as I said, shaders are the big constraint these days. Perhaps the 8600s can redeem themselves with their performance in games.
