However, when the same processor is run at a lower frequency (speed), it generates less heat and consumes less power.
The power consumed by a CPU with a capacitance C, running at frequency f and voltage V is approximately:[5] For a given processor, C is a fixed value.
At the same time, the voltage requirement decreases from 1.484 to 0.956 V. The result is that the power consumption theoretically goes down by a factor of 6.4.
For example, when an operating system is not busy, it tends to issue x86 halt (HLT) instructions, which suspend operation of parts of the CPU for a time period, so it uses less energy per tick of the CPU clock than when executing productive instructions in its normal state.
Microsoft has reported that there may be problems previewing video files when SpeedStep (or the AMD equivalent PowerNow!)