CPU usage while rendering previews

Hi all,

I find it strange that when I render 1:1 previews for raw images from Nikon D800, my overclocked Core i7 3770K @ 4.5GHz is used anywhere from 22%-50% thus completing the render task slower than it really could.

Is it a known issue?

Is the a 'hotfix' for forcing LR4.3 utilizing the full potential of my CPU?

Is it like this for everyone?

I'm using Windows 7 64bit with 16GB RAM.

Thanks,

Gil.