Intel i7 920 ghz keeps changing?

Whenever i am checking my temps or running a benchmark, the speed on the processor keeps jumping around. Anywhere from 1.6 to 2.8 ghz, why is this happening and is this okay/normal?

Normal. It can go up to as high as 2.93GHz at rare occasion when you are under heavy load and need the extra performance, and can go as low as 1.6GHz to save power and make less heat when you aren't doing much.