Processor power management technologies are defined by the Advanced Configuration and Power Interface (ACPI) specification and encompass two primary categories: Power performance states (P-states) and Processor idle sleep states (C-states).
- P-states serve to reduce CPU power consumption by dynamically adjusting the processor’s frequency and voltage, thereby scaling its performance. The number of available P-states can vary significantly across different CPU models, even within the same product family.
- C-states, on the other hand, represent low-power modes where the CPU switches off certain components or functions. These states are designed to further decrease power usage during idle periods. The number and depth of supported C-states can differ by processor model, and some deeper states may not be accessible to the operating system, depending on the vendor’s implementation.
In summary, while P-states focus on adjusting performance to conserve power, C-states enable deeper levels of power savings by shutting down specific CPU functions when idle.