Nvidia GeForce 6800 GS reference card
Real overclocking potential
Review The GeForce 6800 GT was a cracker. While Nvidia wowed everybody with the 6800 Ultra, it was the 6800 GT that most people bought, offering most of the bang without quite as much of the buck.
However, Nvidia has decided that the 6800 GT has had its day. The reason? Well, ATI has been fighting back to compete with the GT. Firstly, there was the Radeon X800 XL, which followed the 6800 GT's blueprint of being a scaled back version of the top-end cards. But then ATI produced the X800 GTO. Unlike the Radeon X800 GT, the GTO is a 12-pipe, six-vertex card running at 400MHz, with 256MB of 980MHz GDDR 3 across a 256-bit memory bus. Over the last couple of months this has been doing damage to sales of Nvidia's 6800 series, though the success of its 7800 series has deflected many from noticing this.
The time was ripe, therefore, for a response from Nvidia and the result is the 6800 GS. Let's get this out of the way from the first: despite having the same five vertex shaders and 256-bit memory interface, the GS has 12 pixel pipelines, four fewer than the 6800 GT. Yet Nvidia claims that the GS is faster than the GT. How is this possible? This is due to the GS possessing much greater clock speeds, with the reference card running at 425MHz core and 1GHz memory, compared to 350MHz and 1GHz for the standard GT. Clock cycles are much cheaper than pipelines and the 75MHz increase ensures that it can compete with the GT despite the reduced number of pipelines.
The reason Nvidia is able to push the cards clock speeds is due to the fact that the GS is a native PCI Express part built on a 110nm process, rather than the 130nm process of the GT, which also needed a separate AGP-to-PCI Express bridge.
Stock clock speeds haven't just increased, however. One of the benefits of the reduced production process is that there's more headroom for overclocking, and we've actually included some overclocked results to get a sense of what impact that has.
Aside from clock speeds the other benefit of the smaller process is that it's cheaper. Smaller chips means you get more on a wafer and as there's no longer any AGP-to-PCI Express bridge chip, the transistor count is reduced further. These cost savings are passed on to the board partner who passes them on to the customer, which is why the GS retail price is able to come in at less than that of the GT. Everyone's a winner!
Power draw is also reduced, with Nvidia stating that only a 300W power supply is required for a single card and 420W for SLI. Of course, as a recent part the GS enjoys all the 6-series goodness such as PureVideo support for improved video playback.
The reference card itself looks very similar to the GT, though to combat the heat produced by the higher clocks the heatsink over the GPU looks to have been replaced with a slightly heavier copper version in place of the aluminium one on the GT. There are DVI and VGA ports on the rear as well as a TV-out. Nvidia has also made the plate covering the heatsink on the card much more shiny: which is nice.
The next great thing about the 6800 GS is that it's available right away from your nearest online retailer. This is becoming something of a pleasant habit from Nvidia and one that puts certain other companies' launches to shame. On that note it's pertinent to mention that the card that we wanted to put this up against was the Radeon X1600, but as we've yet to have any kind of availability date or pricing confirmed we weren't able to do so.
While the X1600 was announced with much fanfare as part of the X1000 series of products, Nvidia was very quiet with the GS, even taking care not to reveal its imminent launch by making sure that there was no mention of the part in its drivers until the last minute.
So onto the scores. Our current graphics test bed still consists of a venerable Athlon FX-55 running in an MSI SLI motherboard with 1GB of Crucial Ballistix RAM. The driver used was 81.87. We retested the GeForce 6800 GT to see if the GS matched Nvidia claims of keeping up with its older but beefier sibling.
Starting with the starting to creak a bit DirectX 8.1 test 3DMark 03, the GS comes in slightly slower than the GT but there's not much in it. Moving to the DirectX 9 3DMark 05, the GS was actually slightly faster, though again there's not much between them, though the 175 points its ahead at 1600 x 1200 with 4x FSAA and 8x AF is worth noting.
Moving on a real game, Far Cry, we see the GS again falling behind the GT, though it's very close, indeed being less than a single frame in most cases. Doom 3 is behind by the same narrow margin while Half Life 2 is up from the GT, though again the difference is minor.
At the sweet spot of 1280 x 1024 with 4x FSAA and 8xAF you'll get around 45 and 55fps depending on the game, which is playable, though you'll probably have to turn it down for online shooters where frame rate is king.
Overall then, Nvidia has indeed produced a card that matches the GT but the good news is that it's available at a lower cost. Overclockers has a standard card from Leadtek on sale for £165, while a GT will cost you £188.
The benefit of the 110nm process should mean more headroom for overclocking so we put that to the test and managed to push it up quite dramatically to 500MHz core and 1.2GHz memory. At this setting 3DMark 05 at default settings went up considerably and there were decent increases in the game tests. Far Cry at 1600 x 1200 went up from 70.1 to 76.3 and at the same resolution Doom 3 gained a healthy 10.5fps. However, this overclock is fairly aggressive and we saw evidence of clock throttling with the scores in Far Cry actually dropping. Such is the unpredictable nature of overclocking.
The GS does what it says on the tin, offering GT class performance but at reduced cost and with real overclocking potential. At around £165 on the street it's looking like Nvidia might be able to claim back that middle-tier performance ground, especially with Shader Model 3 support helping it to outdo ATI on the feature count. With a retail GS board on its way, we'll soon revisit the retail GS against the competion, so be sure to check back in a few days for that.