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NVIDIA's SLI Shortchanges Gamers?

According to NVIDIA’s marketing, NVIDIA’s Scalable Link Interface (SLI) "can deliver as much as 2x the performance of a single GPU configuration for unparalleled gaming experiences." What NVIDIA fails to make clear, however, is that SLI currently requires NVIDIA to write driver profiles for each game to support SLI. Are all the games you want to play supported?

Introduction:

In April of 2004, NVIDIA announced the GeForce 6 series GPUs. In June of 2004, NVIDIA announced their Scalable Link Interface, otherwise known as SLI, and in November of 2004 we previewed it. Since April of 2004, there has been a total of three official non-beta WHQL ForceWare driver releases from NVIDIA. Since we previewed SLI in November, there have been zero official non-beta WHQL ForceWare drivers released. ATI, on the other hand, has a plan to deliver a new CATALYST driver once a month. I think that driver updates may very well be what makes or breaks SLI.

If you aren’t familiar with NVIDIA’s SLI, please read our introduction and preview first, as it is necessary to understand the technology before you read this editorial. In our SLI Upgrade Guide, we examined the performance of the GeForce 6600 GT, GeForce 6800 GT, and GeForce 6800 Ultra in both single card mode and SLI mode using three popular games. We used DOOM 3 which utilizes, naturally, the new DOOM 3 engine, which will also get a lot of use in future titles much as the Quake 3 engine did. We used FarCry, which has been a real test of DirectX9, and recently Shader Model 3.0, performance. Lastly, we used Half Life 2, which has great gameplay, superb graphics, and is also based on DirectX9. HL2’s Source engine will also be getting a lot of use in future titles. This triage of games is a good measure of the gaming experience a leading edge video card can deliver to you. However, if you are a gamer like me, these are not the only games that you play. In fact, I play games from many different genres, not just first person shooters. I also play less “popular” games that I believe could still benefit from SLI.

No SLI for Me?

But what is this? SLI isn’t going to work in my game, you say? Say it isn’t so! Yes, it is so. You see, in order for SLI to work, NVIDIA has to program a profile into the drivers that tells the drivers to run the game in SLI mode. In addition, the profile also tells the drivers to use either Alternate Frame Rendering (AFR) or Split Frame Rendering (SFR). Only certain modes work well in certain games. AFR might be the optimal choice in one game, while SFR might be the optimal choice in a different game. Remember, however, you will not get SLI in a game unless there is a profile in the driver telling the driver what mode to use in that game. If there isn’t a profile, guess what? You don’t get the benefit of SLI in that game. So how can we find out which games support SLI right now? Well, NVIDIA has a nice table on NZone that shows what games and benchmarks (yes, benchmarks) support SLI.

Interestingly enough, NVIDIA has added synthetic benchmark tests to the SLI support list. It's here you will find Aquamark3, 3DMark2003 and 2005, as well as Code Creatures. [SARCASM]It is nice to know NVIDIA is spending their time creating SLI profiles for synthetic benchmarks.[/SARCASM] In fact, out of all the games listed, the total amount of games that are on the shelf now supporting SLI is 15. 15? 15 out of possibly what…thousands of games? NVIDIA also lists the Unreal Engine 3, which isn’t a game at all yet. We won’t see a game based on the Unreal Engine 3 for at least a year or two. They also list a demo, not a full version game.

Real World Game Testing

Well, we decided to do a little testing of our own and see if the games we are playing now work in SLI or not. Some of these games were just released, others are at least a year old. Our testing consists of actually playing the game in question and seeing if there are any real benefits in an NVIDIA SLI setup.

We have compared which games support what SLI mode across three driver sets. By “support,” we mean that we saw the expected image quality benefit from using an SLI setup.

We used the official 66.93 driver, then we used the beta 67.03 drivers available from NZone, and then we used the latest beta driver we could find, which was version 71.24. We wanted to find out if any of the games we are currently playing have SLI profile support between these three driver sets.

Out of the twelve games we tested, we know that seven do not support SLI. We know this because SLI gave us no benefits in the benchmarks or real-world gaming whatsoever. That is, there was no difference between single card performance and SLI performance. Interestingly enough, when turning on NVIDIA’s built in HUD SLI Load meter, it was no where to be seen in our games listed above as having no SLI support or benefit.

There are a few games, however, that could very much benefit from SLI. Need For Speed Underground 2 was released in November 2004, and it is a very GPU intensive game. This game could benefit from the added performance of SLI, yet there is no support for it. The Chronicles of Riddick was just released for the PC, and this game is extremely demanding on video cards, especially in SM 2.0++ mode with soft shadows. This game could also really benefit from SLI, but again, sadly, there is no SLI support (and we are already halfway through the game).