INFO: What is SLI
Scalable Link Interface or SLI is an Nvidia graphics card technology that increases graphics performance by combining multiple GPUs (graphic processor units). To take advantage of this performance enhancing technology, you need a SLI-capable graphics card and a motherboard.
With Nvidia SLI technology, graphics cards can be from different manufacturers, but they need to be from the same GPU series and model name. More advanced SLI-enabled graphics cards can support more than one monitor while providing enhanced graphics performance.