The reason why I'm concerned is the turbo boost monitor used to fluctuate before between 1.6 and 3.4, even when the PC was not running a particular program. Now, it just stick to the bottom without a slightest movement. I ran the OCCT test because of this observation. Also 3dmark 11 used to report 3299MHz for CPU, not 1600, and the physics score is down now.
I don't have any other change except the nvidia driver update.