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NVIDIA's GeForce 6800 GS graphics processor


One more spin on GeForce 6
— 8:00 AM on November 7, 2005

WATCHING THE HIGH-END GRAPHICS scene these days can practically give a miser like me a nosebleed. Six-hundred dollar video cards? Are you kidding? And you're telling me some people are going to buy two and run them together? I'd better sit down for moment.

Fortunately, as technology progresses, computer power does get cheaper over time, and that's certainly true in graphics. Case in point: NVIDIA's brand-new GeForce 6800 GS. This video card, making its debut today, packs the considerable power of a GeForce 6800 GT at the not-so-painful price of $249. Does that combination of price and performance make the GeForce 6800 GS worthy of your consideration? We aim to help you answer that question by flooding you with benchmark results until your head swims and you cry out for sweet mercy. We've tested a number of the latest games, including F.E.A.R, Serious Sam 2, and Half Life 2: Lost Coast. Keep on reading to see how the 6800 GS compares to several of its closest competitors—and whether a pair of these puppies will keep up with one of those six-hundred-dollar monsters.

Gran Turismo versus... Good Stuff? General Smoothness?
If you're like me, you may be a little bit surprised to see NVIDIA cranking out a brand-new GeForce 6-series video card as we head into the holiday buying season, given that the GeForce 7 series has been around for a while in several incarnations. The truth is that the GeForce 6800 GS is not a major new GPU revision in any sense of the word, though, and that the 6800 GT that it ostensibly replaces was most definitely in need of replacement.

The 6800 GS is based on a GPU that NVIDIA has dubbed NV42, and its specs are rather similar to another, already familiar NVIDIA GPU, dubbed NV41. You'll find an NV41 chip lurking under the garishly decorated heatsink of any recent GeForce 6800 (no extended moniker edition) card with a PCI Express interface. Both the NV41 and the NV42 have five vertex shader units, 12 pixel shaders, and eight render back end units, or ROPs. The difference between them is that the NV41 was built by IBM using a 130nm fab process, and the NV42 is built using a 110nm process. Because the two chips are manufactured using different fab processes that rely on different libraries, NVIDIA estimates their transistor counts differently. Thus, the NV41 purportedly has 190 million transistors, while the NV42 has 202 million transistors, although the two chips "are fundamentally the same architecture," according to NVIDIA.

You may be wondering: why would you consider a 12-pipe chip like the NV42 a replacement for the GeForce 6800 GT? The answer is simple: higher clock speeds. Although the 6800 GS has fewer pixel shader pipes, it's practically a dead ringer for the 6800 GT when it comes to key specifications like texel fill rate, thanks to its 425MHz core clock speed. In fact, because I'm still trying to shed those recurring math-class nightmares that plague any liberal arts major, I'm going to hit you with a fancy table laying out those specifications in some detail. This should illustrate how fewer vertex and pixel shaders running at higher clock speeds can make the 6800 GS a pretty close match for the 6800 GT. Of course, these numbers won't produce exactly comparable performance, especially across different generations and brands of GPU architectures, but they're still fairly relevant.


Numbers and stuff

The 6800 GS doesn't quite match up with the 6800 GT in terms of pixel fill rate, but that number isn't terribly important in today's games, which require increasing amounts of shading and texturing power per pixel. The 6800 GS offers slightly more vertex processing power, slightly less pixel shading and texturing power, and exactly the same amount of memory bandwidth as the GeForce 6800 GT. Functionally, they're practically twins.

The NV42, however, has the benefits of youth. The 6800 GT is based on the original NV40 chip, and it needs the help of a separate bridge chip in order to talk over a PCI Express interface. NV40 silicon is also incapable of accelerating WMV video decoding. The NV42's smaller transistor count and newer fab process should allow the 6800 GS to draw less power and produce less heat than the 6800 GT. The 6800 GS is quite likely cheaper to manufacture, as well.

The card
As you'd expect, the GeForce 6800 GS needs only a single-slot cooler to keep it happy. The board design looks very similar to other GeForce 6-series cards, especially the GeForce 6800 cards based on the NV41.



My only quibble with the NVIDIA reference design pictured above—which is the card we tested—is the lack of a second DVI output. I think a $249 graphics card ought to have a pair of digital outputs. Heck, I think a $149 graphics card should, too. Let's hope some of the board makers producing 6800 GS cards decide to do the right thing and convert that VGA output into a second DVI port.

So... who's the competition?
In order to compare the GeForce 6800 GS with its closest competitors, we've had to stare deep into the soul of the video card market and pick out a couple of names from the crowded space around the $249 price point. If you were going to spend about that much on an ATI graphics card right now, you'd more than likely be looking at a Radeon X800 XL. You can find the X800 XL selling at online retailers for a prevailing price of about $259, although there are a few places selling the X800 XL for less. This 16-pipe card started life as a foil to the GeForce 6800 GT, so I suppose it's fitting that it should now face off against the 6800 GS.

There's also ATI's new generation of graphics cards, the Radeon X1000 family. Due out at the end of this month is the Radeon X1600 XT with 256MB of memory, a card that ATI says will list for $249. That should make it a direct competitor to the GeForce 6800 GS, but I'm not so sure about that. We've included it in our comparison for the sake of fairness and completeness, but the X1600 XT just doesn't look to me like a $249 card. Everything about it, from its teensy GPU die size to its four texture units, four render back ends, and its 128-bit memory interface screams "cheaper!"—like $169 or so. The X1600 XL looks like it's outclassed by the likes of the 6800 GS or even ATI's own Radeon X800 XL. ATI has blessed the X1600 XT with twelve pixel shaders and a stratospheric 590MHz clock speed, though, so perhaps it's not completely out of its league. We shall see about that.

We have also included a wide range of higher-priced graphics cards from ATI and NVIDIA in our testing today, in part because they're competing directly with an intriguing option: a pair of GeForce 6800 GS cards in SLI. Could buying two of these new cards and running them in tandem be more cost-effective than ponying up for ATI's new Radeon X1800 XT? Maybe so.

We've also included a range of cards because it was time for an update since we did our last big graphics comparison in our Radeon X1000 series review. Both major players have released new drivers since then, claiming big performance gains, and several excellent new games have arrived, as well.