Acronym for Scalable Link Interface. nVidia's technology released in 2005 enables the user to run dual video cards in PCI-E slots for improved graphical performance. Ideal for avid PC gamers when one video card just isn't enough. Rival ATI came out with similar CrossFire technology that year. In 2006 Quad SLI technology was introduced and showcased on Dell's limited edition XPS 600 Renegade which had the power of four video cards, unnecessary at the time.
Dude, I just ran Oblivion at 80 fps with SLI mode.