A SLI video card is a video card that allows you to insert more than 2 graphics cards into your computer. It supports up to 4 of the same GPU's running at the same time. SLI was developed by 3DFX in 1997 for use with their graphics card the Voodoo2 but after the company was defuncted nVidia acquired the rights to use this technology. There is also CrossFireX which was developed by ATI.

SLI stands for Scan Line Interleaving (also alternatively Scalable Link Interface). It is a technology which connects 2 PCI or PCI-E cards from the same company, by an internal cable connection.The graphics processing and displaying is divided among these two cards. One card processes and displays the odd number fields while the other handles the even number fields. It gives double fill rate performance to Voodoo2 and are fast.

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