NVIDIA's GeForce 6 SLI: Demolishing Performance Barriers
by Anand Lal Shimpi on November 23, 2004 10:23 AM EST- Posted in
- GPUs
Half Life 2 Performance
Given our recent focus on Half Life 2 performance, it should be no surprise that we start off our performance coverage with Valve’s latest title. The benchmarks we used for this review were created in house and are all documented (as well as available for download) in Parts 1 and 2 of our Half Life 2 GPU Roundups. One word of caution however, the benchmarks in those reviews used NVIDIA’s 67.02 drivers, however those drivers in particular do not yet have SLI support, thus we were forced to use older 66.93 drivers for this review – thus making our NVIDIA Half Life 2 numbers not directly comparable between these reviews.
Half Life 2: AT_canals_08
In this first demo we notice a couple of things; for starters, there is a small but consistent performance drop when enabling SLI. The reason behind this performance drop is because at lower resolutions we are still CPU limited with the higher end 6800 based GPUs, thus the additional overhead of splitting up the rendering and forwarding data from one GPU to the next for recombination ends up making SLI slightly slower than just a single GPU. That being said, no one would realistically have $800+ worth of video cards and run at 1024 x 768.
Looking at 1280 x 1024 there begins to be more of a performance benefit to SLI, but the benefits are not really significant until we hit 1600 x 1200. At 1600 x 1200 the 6800GT and Ultra are still somewhat CPU limited, but the 6600GT is far from it. Moving to two 6600GTs increases performance by 67% and delivers higher performance than a single 6800 Ultra, 9.5% faster to be exact. This scenario alone showcases the upgrade potential for SLI; purchasing a single 6600GT today allows you to run Half Life 2 at 1024 x 768 quite well, but adding a second card later on will let you run at higher resolutions (or more GPU intensive games). Assuming you can add that second card later on for less than you purchased the first one, your upgrade path actually puts you in a better situation overall than had you just purchased a single, more expensive card at the start. Keep an eye on this comparison between two 6600GTs and a single 6800GT/Ultra to evaluate the mainstream upgrade path benefits of SLI.
With 4X AA and 8X AF enabled, the situation changes dramatically. Although the performance gains are impressive, the pair of 6600GTs isn’t able to outperform a single 6800GT/Ultra. For 6800GT/Ultra owners, SLI enables smooth playability at high resolutions with AA and AF enabled. We play tested much of Half Life 2 with two 6800GTs at high resolutions with AA/AF enabled and for the most part the game was butter smooth; at 1600 x 1200 with 4X AA/8X AF enabled however there were some areas where even two 6800 Ultras would get choppy. But most resolutions and settings that were not smooth before on a single card were definitely playable thanks to SLI.
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CrystalBay - Wednesday, November 24, 2004 - link
#61 good point, I also wonder how well it runs at super high resolutions...PrinceGaz - Wednesday, November 24, 2004 - link
We've seen profiles for many games in nVidia drivers since the 5x.xx series, I expect the SLI mode is just something they've added to it for when the card is running in an SLI mode. If in doubt, I'd have thought SLI AFR will be fine for most games that don't have a profile defined (assuming you can choose SLI mode), or SFR for those games that use motion-blurring (usually certain types of racing games).Pampero - Wednesday, November 24, 2004 - link
where in the review talk about the profiles?Is there a list of the games that can enable SLI?
Gatak - Wednesday, November 24, 2004 - link
Where is the 2048x1536 tests? It is clear that 1600x1200 is no match for the SLI setup in most games. Why not do testing at higher resolution.If 2048x1536 ran smoothly, Then the demand for better monitors would be stronger - giving manufacturers reason to make better monitors for us =).
PrinceGaz - Wednesday, November 24, 2004 - link
#55- If SLI is only able to be used on games nVidia have profiled like you say, and that the user cannot themselves force it to run in SLI AFR or SFR mode, then that's a serious problem for people who play non-mainstream games who might be considering SLI.After reading this article, I now believe more than ever that the only people who should be seriously considering SLI are those who are willing to buy two 6800GT or 6800 Ultra cards in one go, in order to have a top of the range system. The upgrade option doesn't make sense.
Anand didn't compare the costs of an SLI upgrade against a non-SLI upgrade; instead he compared buying a second 6600GT later on when they're cheaper, to buying a high-end card initially and *not* doing any upgrade. Of course it's going to be more expensive if you buy a high-end card from the outset.
The true upgrade alternative is that instead of buying a second (now cheaper) 6600GT to achieve roughly 6800GT performance, you would sell your 6600GT while it can still fetch a good price and put the money towards a (now also cheaper) 6800GT or maybe a mid-range next-generation card that has the required performance. When you look at how much prices fall on high-end cards when something even a little faster comes out, pushing them nearer to mid-range cards; it should be obvious that replacing the card with a faster one is a more cost-effective option for anyone considering an upgrade at a later date, than buying a second identical card on top of the one you already have.
Yes there's the hassle of selling your first card, but not only do you have total flexibility over what you upgrade to (with SLI you have none); you also don't need an SLI mobo, you won't have two graphics-cards generating excess noise, and you'll have a lot more PCI/PCI-e slots left free for other cards.
bob661 - Wednesday, November 24, 2004 - link
IMHO, SLI is for people like me and also for people that need to have the latest and greatest. People like me don't upgrade every 3 months, 6 months, or even a year. I upgrade every 2.5 to 3 years. It would be nice to be able to run 2006 or 2007 games on 2004 technology. Who knows, this might extend my upgrades to 4 years. ;-)Momental - Wednesday, November 24, 2004 - link
#56 I would imagine that nVidia is aware of this and who knows, they may implement a utility within their driver that automatically flashes the BIOS of the "older" card, if one is detected. Either that, or they could write something into the driver to search for another GPU and once it's found, ask you if you would like to flash its BIOS upon restart. And voila!The fact of the matter is that it's way too early to speculate as to whether or not SLI is a viable and cost-effective solution. Something tells me that it will be because it's not like the "next big thing" ie: cards that are twice as fast, are right around the corner. If they were, then I'd say 'no'. It isn't worth it for reasons stated by #42.
nserra - Wednesday, November 24, 2004 - link
I think the issue of the card to MUST have the same bios is ENORMOUS. So the buy one now and buy the other LATER will "not" be possible. I doubt that a year old card has the same BIOS of brand new one.Too much “issues”…
nserra - Wednesday, November 24, 2004 - link
I think the issue of the card to MUST have the same bios is ENORMOUS. So the buy one now and buy the other lather will "not" be possible. I doubt that a year old card has the same BIOS of brand new one.Too much “issues”…
Elliot - Wednesday, November 24, 2004 - link
I want one of this SLI boards but the article said that you can force the driver to enable SLI on games without profiles on Nvidia drivers but this is not real.If no SLI profile exists for a game, there is no SLI rendering. It is not possible to force SLI mode or generate your own profile. According to NVIDIA however the driver already contains over 50 profiles for games running with SLI. For newer titles this therefore means that SLI system owners have to wait for a new driver. But even then there is no guarantee that SLI will be possible with a particular game. So this is not very good news.