SLI overview:

NVIDIA's Scalable Link Interface (SLI) technology allows two or more graphics processor units (GPUs) to be linked cooperatively and run together as if they were a single faster GPU.
 
For some graphics-intensive games, SLI may offer a performance boost, may allow higher display resolutions, and may make it possible to turn on more graphics-intensive game features without degrading the game's frame rate. Frame rate is a measure of how frequently the game's screen image is updated, usually specified as a number of frames per second (fps). If the frame rate is too low, game action will not appear smooth and continuous, and may even be similar to watching a slide show.

SLI may also improve the performance of graphics-intensive applications other than games.

For computers with two GPUs, like those in the Applicable Models list above, the increased video performance from the computer's SLI graphics subsystem will typically be less than 2X that of a single GPU. The degree of performance increase varies from one game to another, and also depends upon the particular configuration of each game’s features. For some games, SLI provides only a very slight performance increase,. For other games, SLI may slightly decrease some aspects of game performance .

There are several SLI performance modes, including a Single-GPU mode that essentially turns off SLI.

Determining SLI support for a game: For a game to take advantage of SLI, an Application Profile for that particular game must be present in the display driver. Follow these steps to view the list of Profiles for games and other applications present in the currently-installed display driver:

1. Right-click the Window Desktop, and then click NVIDIA Control Panel.

2. Click 3D Settings.

3. Click Manage 3D Settings.

4. Click the Program Settings tab.

5. Scroll through the Programs list shown in the screen shot below.

The games in this list will use SLI automatically, without requiring any configuration. 

Upgrading the display driver : If you have a game or other program that is not on this list, try upgrading the display driver for your computer. Newer version of the display driver may include additional Application Profiles.

For general assistance with downloads, see Support Bulletin 98081213 Obtaining downloads and support docs from the Toshiba Support website.

Creating a custom Profile: You can also create your own Application Profiles to add SLI support for games not included in the list from the display driver. Click the following link for detailed steps on the NVIDIA website.

GPU vs CPU:
Graphics processing power (from the GPU) is most critical at higher display resolutions. At lower display resolutions, other factors become more significant, especially the computer's CPU -- which is often used to do the math for modeling physics (a rock rolling down a hill, smoke drifting out of a chimney) and for artificial intelligence of game characters.

At any resolution, SLI will often allow you to enable a greater selection of a game's graphics-intensive features (such as shadows, antialiasing, HDR) without suffering a severe performance penalty.

In addition to SLI, there are many ways to increase a game's frame rate and overall performance, including installing additional memory, lowering the display resolution, adjusting other game settings, 'defragging' the hard disk drive, closing other applications, and shutting down non-essential processes.

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