Older NVIDIA SLI™ based products can only support a Dual display within SLI mode. However, GTX 200, 400, and 500 series graphics cards can run up to three monitors when ran in SLI using Nvidia 3D Vision Surround. The 600 series and newer cards that can support 3 or 4 monitors do not require SLI to run 3D Surround, but may be run in SLI for increased performance. Please note that not all cards in all series can run in SLI. For the complete list of system requirements and how to connect your monitors please visit:

https://www.nvidia.com/object/3dv-system-requirements-surround-technology.htm