Notes about Intel Enhance SpeedStep Technology
本文将mark下Intel Enhance SpeedStep Technology的相关notes。
Overview
Enhance Intel SpeedStep Technology enables operating system to control and select P-state, it allows the processor to lower the speed when it is in idle or low workload, this will allow the system to save power consumption.
Key features
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.
- 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(处理器内部控制电压升降速率，确保无毛刺平滑转换).
Because there is low transition latency between P-states, a significant number of transitions per-second are possible.
Spec
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