Sunius said: What is your power supply unit? What is your monitor resolution? What drivers are you using?
Sunius said: Are both PCIe power connectors connected to the graphics card??
Sunius said: Also is this a new PC or did you upgrade some parts and kept some old parts?
Sunius said: Did you reinstall windows when you changed CPU? If you did not, I can give you 90% that it is the problem why bf3 is running so slow.
Sunius said: I'd try redownloading the game, maybe even reinstall of Origin.