Asus p6x58d premium after bios upgrade i get less graphic performance

Hello, today i had some "loss" of ram out of nowhere... have 12GbB but it only recognized 8. try to solve it in the bios and some forums and some say to upgrade the bios rom. So i got the 1501 version and, voilá! it rocked!! but then... oops... somehow the graphic performance whent down the drain... (gtx670) had 120fps on CodBlackOps2 (full extra graphics) and now it's down to 22?!?!?!
Can some1 tell me what to do?