Lots of great info in this thread. Both the user benchmark results and the service manual indicate that the 3612QM and even the 3520M are stock configuration processors, so I think either of these and even the 3540M you were originally considering would all work.sorry for mistype my current processor is i3 -3120M (lenovo G580 20150). Is it upgradable to i7 3612QM (both processors are of 35w).