How to enable or disable NVIDIA SLI mode
Open the NVIDIA Control Panel, as shown in the example image below. This can be accessed through the NVIDIA icon in the Systray, through the Windows Control Panel, or through the advanced section of your display properties.
Once in the NVIDIA Control Panel, click the Set SLI configuration link on the left. Then, either select Do not use SLI technology or Enable SLI technology (recommended) to disable or enable SLI.