Overview of Enhanced Intel SpeedStep® Technology for Intel® Processors

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Product Information & Documentation

000007073

09/01/2021

Enhanced Intel SpeedStep® Technology enables operating system to control and select P-state.

The following are the key features of Enhanced Intel SpeedStep® Technology:

  • Multiple frequency and voltage points for optimal performance and power efficiency. These operating points are known as P-states.
  • Frequency selection is software-controlled by writing to processor model-specific registers (MSRs). The voltage is optimized based on the selected frequency and the number of active processor IA cores.
    • Once the voltage is established, the Phase Locked Loop (PLL) locks on to the target frequency.
    • All active processor IA cores share the same frequency and voltage. In a multicore processor, the highest frequency P-state requested among all active IA cores is selected.
    • Software-requested transitions are accepted at any time. If a previous transition is in progress, the new transition is deferred until the previous transition is completed.
  • The processor controls voltage ramp rates internally to ensure glitch-free transitions.
  • Because there is low transition latency between P-states, a significant number of transitions per-second are possible.