Chapter 3. Core Infrastructure and Mechanics
cpupowercommand featured in this chapter, ensure you have the cpupowerutils package installed.
3.1. CPU Idle States
- the operating or running state. In this state, the CPU is working and not idle at all.
- C1, Halt
- a state where the processor is not executing any instructions but is typically not in a lower power state. The CPU can continue processing with practically no delay. All processors offering C-States need to support this state. Pentium 4 processors support an enhanced C1 state called C1E that actually is a state for lower power consumption.
- C2, Stop-Clock
- a state where the clock is frozen for this processor but it keeps the complete state for its registers and caches, so after starting the clock again it can immediately start processing again. This is an optional state.
- C3, Sleep
- a state where the processor really goes to sleep and does not need to keep its cache up to date. Waking up from this state takes considerably longer than from C2 due to this. Again this is an optional state.