To run NVIDIA Multi-GPU

Running NVIDIA Multi-GPU configuration gives improved rendering performance in your Direct3D and OpenGL applications.

Note: To use this procedure, your system must have two or more NVIDIA GPUs connected to two or more displays.

From the NVIDIA Control Panel navigation tree pane, under 3D Settings, select Set Multi-GPU configuration to open the associated page.
Under Select multi-GPU configuration, click Maximize 3D performance.

The GPU configuration visualizer shows the pending multi-GPU configuration as well the display connections and enabled state of the displays. The multi-GPU bar points to the GPUs that are working together to increase rendering performance.
Click Apply.

If you have more than one display connected,

Windows XP or pre-GeForce 8 series GPUs

You can select which display to use to view your game. Use the Set up multiple displays page to select with display to use as the primary display. The GPU connected to this display will function as the "primary" GPU, all others will function as slaves to the primary GPU.

If none of the displays in the multi-GPU group are the primary display, then the driver will select which display to use to view multi-GPU accelerated games.

Windows Vista or later, and GeForce 8+ series GPUs

You can select which display to use as the focus display, or the display to which you want to apply full SLI acceleration for full-screen applications. Use the Set up multiple displays page to select which multi-GPU display to use as the primary display. This becomes the multi-GPU focus display.

If none of the displays in the multi-GPU group are the primary display, then the driver will select which display to use as the multi-GPU focus display.