Asus Crosshair V Formula/ThunderBolt - Manual (Page 190)

5-8 Chapter 5: Multiple GPU technology support
B4. Select the NVIDIA GeForce tab, and
then click Start.the.NVIDIA.Control.
Panel.
B5. The NVIDIA Control Panel window
appears.
Enabling.SLI.settings
From the NVIDIA Control Panel window,
select Set SLI Configuration. Click
Enable.SLI and set the display for
viewing SLI rendered content. When
done, click Apply.