a processor running in any other c state is idle higher c state numbers represent deeper cpu sleep states at higher c states more components shut down to save power some components that are shut down include stopping the processor clock and stopping interrupts the cpu power states c0 c3 are defined as c0 is the operating state c1 often known as halt is a state where the processor is not executing instructions but can return to an executing state essentially instantaneously all acpi conpornant processors must support this power state some processors such as the pentium 4 also support an enhanced c1 state cie or enhanced halt state for lower power consumption c2 often known as stop clock is a state where the processor maintains all software visible state but may take longer to wake up this processor state is optional and c3 often known as sleep is a state where the processor does not need to keep its cache coherent but maintains other state some processors have variations on the c3 state deep sleep deeper sleep etc that differ in how long it takes to wake the processor this processor state is optional in some implementations the device may be configured in such a way that in computational domain a 301 the device has the highest operating performance point opp of cpu0 with all other cores being enabled in computational domain b 302 the device may have the lowest opp of cpu0 with some of the other cores being disabled as noted in some implementations the device may be configured to wake up from sleep mode.