NVIDIA has changed the way it approaches 3-way and 4-way SLI support for the GeForce GTX 1080 and GeForce GTX 1070. Now out of the box you can enable 2-way SLI by using either an SLI HB bridge (recommended for certain high resolutions), or even a classic 2-way bridge, 3-way and 4-way SLI will be restricted to a few non-gaming apps.
When the GeForce GTX 1080 and GTX 1070 were launched NVIDIA said it would officially not support 3-way and 4-way SLI for Pascal GPUs, however they setup a ‘SLI enthusiast key” webpage, from which enthusiasts can obtain a software key that unlocks 3-way and 4-way SLI support using classic bridges. So all NVIDIA would have to do was optimize a driver for 2-way SLI and then a gamer would get lucky if the game developer added in 3-way and 4-way SLI support. Well that is not the case anymore.
NVIDIA has reportedly removed the entire “software” key process of unlocking 3-way and 4-way SLI support. Now you should be able to enable SLI or 3-4 GPUs, but only a list of apps selected by NVIDIA will be able to take advantage of any 2+ GPU setup. These apps include popular benchmarking tools like Ungine Heaven, 3DMark FireStrike, and Catzilla. NVIDIA could possibly update this list with future driver updates.
I guess NVIDIA’s thinking behind this is to appease overclockers who only care able the score a benchmark spits out. This way they will not have to deal with complaints from gamers about choppy display output.