Do you have advanced physx enabled? It should be in the game options menu. That was the cause for me on my 780ti. Turning it off fixes fps. There is a way to fix this. If you go the nvidia website go to drivers and download the latest physx drivers it should fix it and you should be able to play with the advance physx on. Well this method fixed it for me fingers crossed it fixes it for you.
It would help to try at least three games, as well as a benchmark utility.
It MAY be the PhysX issue but I'm not familiar with that. I do know I had to reinstall my NVidia drivers as PhysX was oddly missing.
You should also mention WHICH GAME as it may be a game-specific issue.
It's metro last light I'm talking about. For me it was pure blind luck that fixed it. I had trouble with metro 2033 which turned out be missing physx driver issues. I was told to download the physx drivers seperatly. Which fixed metro 2033 tried metro last light and boom advanced physx low fps issue was fixed for me.
Let us know how it's going, and if you've reinstalled the drivers and verified that PHYSX is in the list of what's being installed. If you don't choose "EXPRESS" you can view what components are being updated and PhysX should be there.
Batman Arkham City has an issue that often requires you to temporarily use an earlier version of your NVidia drivers. If the game crashes just as you are about to defeat Mr. Freeze then you have to:
a) Uninstall, then install the earlier version (can Google for which version)
b) Finish that area and SAVE the game
c) Update to latest drivers and continue.
It about sums it up. It's a physx driver issue. Apparently somehow Metro LL reverts whatever physx driver you have to an older one that causes the low fps. Simply replace that and you should be able to enjoy physx enabled. I just tried it and went from 3-5fps min to 19fps as my new min
Also it went from virtually unplayable and horribly laggy to brilliantly beautiful to watch!