Hello,
My configuration :
GTX 760
i7 4771
12Go Ram
I compared my fps on 32 bits and 64 bits version. I've played exacly on the same mission, on the same point of view.
FPS on 32 bits : 44
FPS on 64 bits : 102 OMG
That is normal ?
When I see your tests where you get 2-3 fps, I find my results stranges. I guarantee you this is the truth.
Sorry for my english, I'm french.