SLI is not really a new concept, its actually quite old. It was first used if i remember correctly by another gpu company, 3dfx if im not mistaken. But it did not get very popular due to the technology back then, the card were very large combining 2 monster cards made it extremly difficult to use, no mainstream user would buy something that would not fit in their case. Later on when Nvidia bought 3dfx they got the rights for SLI too, and they improved on it, they made smaller cards with more power so this time SLI is here to stay, and the motherboard companies know this and support SLI with their PCI-E motherboards.
edit: i was unsure if it was 3dfx or some other company so i did a little search and came up with this. Its a good read, it explains how the 3dfx SLI(Scan Line Interleave) and how Nvidia SLI(Scalable Link Interface) work. http://www.neoseeker.com/Articles/Ha...s/nvsli/2.html
