Years and years ago there was a terrific bit of software called Flight Unlimited. It had a CPU intensive flight model that really made a computer work up a sweat. The company tried to develop a combat version; but even workstations couldn't do it.
It hasn't been much of an issue in recent years until decent physics models started showing up in games. Video cards started doing physics equations partly because the cpu couldn't do them all.
Intel's next gen processors should be able to pull it off. So if ATI and Nvidia ever stop slagging each other over which physics program is the best, games will be able to take a huge jump forward in the immersiveness of the environment.