This new model is, like the 4850 and 4870, based on RV770 silicon, but in its tamest form yet. Yes, folks, the great product segmentation game continues with yet another chip having perfectly good—or possibly totally flawed—bits and pieces deactivated to maintain a neat separation between models. On the 4830, two of the RV770's 10 SIMD units have been disabled, reducing shader power (and likely performance) somewhat. Since those SIMD units are tied to texture management units, the GPU's TMU count has dropped proportionately. The end result: the Radeon HD 4830 has a total of 128 shader execution units—or 640 stream processors, in AMD parlance—and can filter up to 32 textures per clock.

That's it for the neutering, though. The 4830 keeps all four of the RV770's render back-ends and associated memory controllers intact, leaving it with an aggregate 256-bit memory interface. The card's GPU core runs at 575MHz, and it comes with 512MB of GDDR3 memory clocked at 900MHz (or 1800MT/s, for those of you keeping score at home.)

Generally speaking, the 4830 proved to be a bit faster than the 9800 GT in our quick round of tests. In terms of overall performance, the contest between the two cards is close enough that, yes, going to a higher-clocked variant of the 9800 GT could potentially tip the balance in Nvidia's direction—perhaps. But there are cases like Quake Wars, where the 4830 matched the more expensive GeForce 9800 GTX+, in which even a generous clock speed boost wouldn't allow the 9800 GT to keep up.

The performance gap at the $120-$130 price range for a target resolution of 1680x1050 between the 9800 GT and the 4830, in practical terms, isn't that much. Both are playable in the majority of games we tested. The exceptions are Age of Conan and Crysis which can get by at 1280x1024 (or with decreased quality settings). While you may get a smoother experience on the AMD card in general, you won't get a significantly more playable experience in most cases in the games we tested.

If the rebates trail off and/or don't favor the NVIDIA part, we've got to lean toward recommending the Radeon HD 4830. AMD's card also supports 8-channel LPCM over HDMI and can handle some games at 1920x1200, making it the cheapest viable option capable of dual purpose use for games and movies on an HDTV and 7.1 surround sound setup. But it's a really close call here.