I'm sure many of you can remember the days of 3dfx, the first Voodoo Graphics back in 1996 and about a year later the introduction of the Voodoo2. Voodoo2 actually made sure that 3dfx reigned supreme for quite some time as two cards could be combined in something called an SLI, Scan Line Interleave, configuration. Each card rendered half of the image scan lines which resulted in double the performance of a single board and the ability to play OpenGL games such as Quake 2 in a 1024x768 resolution. To date no manufacturer has come up with a similar concept simply because modern graphics accelerators are all AGP based, there's no dual AGP motherboards and PCI simply doesn't have the bandwidth to handle modern graphics accelerators. With the arrival of PCI-E things have changed though, a number of workstations motherboards featuring the Tumwater chipset will have dual PCI-E-x16 slots making dual graphics accelerators a possibility again. Nvidia steps up to the plate today with the re-introduction of the SLI concept on the GeForce 6800 series, again using the SLI moniker but now with a different approach to the same principles that made Voodoo2 SLI a huge success.

Update: Official details from NVIDIA here.