You haven't said what your cpu is. If you look at individual threads while moving around you will see most threads are very lightly loaded so although the cpu is only running at a lowish percentage, one thread is running at or near max.

One way to speed things up is try another display style. In the standard ui setup there is the display style pallet at the bottom left corner, a set of orbs. The default is texture shaded, but smooth shaded might the ok for your use, and using this or one of the other styles might help you.