Well all of those are fesible ideas. but I doubt its the proc. Im banking on drivers. I dont have fallout so I cant test. So if it is drivers Im not sure which suite is the good one. you can try altering the drivers to see if it fixes the problem. in NVCP go to manage 3d settings. multiple GPU rendering mode and change it to one of the 2. i personally find 'alternate frame rendering 2' is better. but yMMv now along with or seperate you can adjust the amount of pre rendered frames a little further down. I find upto14 works in most cases as a max. I usually go from 4-6 depending on how it works with the majority of my games. so try one or both of the above. tinker around and see if it fixes it before you try new drivers.