SLI software

For SLI testing, we used NVIDIA’s ForceWare 66.93 driver which is currently available on NVIDIA’s website. This is the driver NVIDIA has certified for use with SLI, which is the reason why we decided to go with it rather than the newer ForceWare 67.02 driver.

Once you’ve got all the hardware needed for SLI up and running correctly, the ForceWare driver will prompt you that your system is SLI-capable. At that point, all you have to do is click the checkbox to Enable SLI and reboot the system, once that’s complete the system will come up again in SLI mode.

It’s important to note that NVIDIA’s cooling solutions for their GeForce 6 cards (including the 6600 GT and 6800 GT) are ducted designs that rely on nearby air for additional cooling. Because of this, the “Slave” card, which is located on the bottom in an SLI configuration (nearest to the PCI slots), will run cooler than the “Master” primary card, we even noticed this when the bottom PCI slot was populated with a sound card. This is because the slave card has access to more fresh air than the master card. Remember, sitting between the master and slave cards is the nForce4 chip.

ASUS also placed both PCI Express x1 slots between the two cards, so if you planned on running SLI with two GeForce 6800 Ultras, it probably wouldn’t be a good idea to populate either of those slots with an x1 PCI-E device.

NVIDIA continues to provide hardware monitoring functionality for SLI users. Just select the card you want to look at, and the driver will tell you its temperature. You can’t however overclock the graphics card’s individually; they must be overclocked as one unit, just as if you had a single card installed.

Unfortunately, NVIDIA doesn’t allow users to toggle between AFR and SFR modes. As you probably know, for some time NVIDIA has had custom profiles for many popular games on the market today. The driver uses these game profiles to determine which game you’re launching, and automatically selects the appropriate SLI mode NVIDIA has decided for that game.

For those who do want to see SLI in action, NVIDIA provides a load-balancing option in the driver. Once checked, you’ll notice a green horizontal bar running across your screen and a second vertical bar that runs from the top to the bottom of your monitor.

Far Cry utilizes SFR

Horizontal bar is lower here

Now the bar is slightly higher

In SFR mode, the thin horizontal bar will dynamically move up and down your screen. This shows you in real time the split between the master and slave cards, as the upper portion above the line depicts the master card, while the area underneath the line is the slave card.

DOOM 3 uses AFR

More load in this scene

In AFR mode, the horizontal bar is static and located across the middle of your screen. Instead the vertical bar adjusts up and down your screen, indicating the current graphics load. When the vertical bar is filled, the cards are running at their optimal load for peak performance.