I just installed a 2nd GTX 1080 and did the standard SLI setup. I fired up Fallout 4 and my FPS difference seems to be minimal at best. At 4K, went from 40 - 45 fps on 1 GPU to only about 45 - 55 fps on 2 GPUs. I am using an HB SLI bridge. I have seen much greater gains from other people... From everything I've gathered, I should be hitting 70+ easily. I DONT GET IT. Both GPUs are running, so I think have SLI setup correctly. I'm running an I7 6700K OC'd at 4.6 ghz and 64 GB of RAM. So, I don't think I'm bottlenecking. I'm confused. I ran 3D Mark to verify I was getting both GPUs firing correctly, and they seem to be as my score doubled (9903 in Firestrike Ultra). I know FO4 is not well optimized, but after seeing other people's results, I must be doing something wrong. Any ideas would be greatly appreciated. Thanks.