SOME IMAGES MAY NOT SHOW UP IN THIS REVIEW DUE TO A LOSS IN DATA DURING A MIGRATION PROCESS, SORRY FOR THE INCONVENIENCE.

Today I will be reviewing 2 Geforce 8800 GTX's in SLI, under various games and benchmarks, to show you if owning more than one graphics card is really worth all the hype produced by it's owners, and Nvidia.

I would first like to also explain what it does to people who are interested in gaming on PC's, and do not know what SLI is, or what benefits, if any it brings to your games. However this article still requires a basic understanding of computer hardware, and related terminology.

Back in June 2004, Nvidia announced that it would bring SLI back into the computer market, which was previously only used by 3DFX before it was aquired by Nvidia. SLI stands for Scalable Link Interface, and differes from the method used by 3DFX. 3DFX SLI stands for Scan Line interleave, which is explained further in the artcile.

So what exactly is SLI?
SLI is basically using more than one graphics card (usually 2), at once to display the graphics on your PC. This means that you have in theory, nearly 2x the power of 1 card working to bring you amazing graphics, which might have been unattainable with one card.

3DFX as mentioned before was the first to use a SLI system with the Voodoo 2. 3DFX used a system which had one card render one line, and the other card the next.

Below is a rough idea of how it worked. One card worked on one set of lines, the other card worked on the rest (hence the name Scanlines, like on analog TV's)

However Nvidia has come up with a superior system for SLI, and has since used it in many cards since the Geforce 6 series was released.

With 3DFX to get the 2 cards connected, you had to use a analog pass through cable to get SLI working. With Nvidia's solution you plug both cards into your 2 PCI-Express slots, and then using a connector which comes with the motherboard, you plug it into the connectors on the graphics cards side, providing a digital, physical link between both cards.

Nvidia SLI modes:

There are three different types of SLI modes you can choose from in the control panel. These are SFR, AFR1, and AFR2.

SFR:

SFR stands for Split Frame Rendering, as of yet not many games support this. Basically what this does, is directly split the frame into two halves, and gives a section to each card. It's not always a 50/50 split, with a complicated algorithm it will share the load automatically when needed.

This is the most CPU intensive of the SLI Modes. However it has a benefit of having 0 latency, just like a single graphics card.

AFR1:

AFR stands for Alternate Frame Rendering, and it's exactly how it sounds. One card renders a complete frame, the 2nd card renders the next frame. It's the least CPU intensive of the SLI modes, however there may be a increase of latency. The latency you will notice is that your mouse movements may not appear as instant as they usually do, but hardly anyone ever notices the difference. I haven't noticed any difference in any tests i have done.

AFR2:

As above this is simply Alternate Frame Rendering, but with some compatibility flags added on top of the normal AFR, providing a greater range of compatibility among games.

The above may sound confusing, and a lot of work to play your games with improved framerates, but if you do not fancy doing the hard work, you're in luck! Nvidia already did most of the work for you, by that each game has a special profile which has a recommended SLI setting for said game. If a new game comes out, usually a driver is released which adds the game to the profile list. Not 100% of games are added though, and you will need to try different settings to see what works and what doesn't.