Isn't this thread about laptops? The iMac system definitions work differently. You will see one P-state that's low frequency, and a range of maybe 4 or 5 that are the fastest ones supported for the processor. When one regularly samples the "current" frequency, and graphs it, that will show very high frequency numbers. But the processor is still regularly going into the lower frequency state, and the power consumed will be much lower than full load power, at idle. That's just how Apple likes to do it on the iMacs, apparently.