Have you tried defragging the folder of which ac is located in? What about reinstalling the game(because there could be corrupted files of such). Are your drivers up to date? If you have this game on steam then try verifying the chache integrity by right clicking the game on steam; go to properties, third tab is local files and you cand defrag, verify the integrity from there.
Oh an i forgot to mention, have a try and run some benchmarking tool like 3dmark and instead of using the settings through nvidia have a try using the in game options to see if it makes any kind of differnce.