Intel Enhanced SpeedStep technology

Enhanced SpeedStep technology is a feature that reduces processor power consumption by automatically lowering frequency and operating voltage when maximum processor performance is not required or saving battery power is more important. First microprocessors with Enhanced SpeedStep technology, mobile Pentium III-M and Pentium 4-M, included only one low-frequency state. More recent mobile microprocessors have multiple low-frequency states with different operating frequencies and core voltages. Having multiple states provides better balance between battery power savings and required performance, and allows the CPU to shorten processor downtime during state change (CPU is not operational during when transitioning from one state to another, and changing the state from the lowest frequency mode to normal mode takes most of the time).

Enhanced SpeedStep technology was implemented in Intel microprocessors. AMD microprocessors have somewhat similar feature called PowerNow!.