System Sleep States: S0, S1, S2, S3, S4 & S5

The overall power consumption of the system is referred to as System Power States. There are a total of six different power states ranging from S0 (the system is completely powered ON and fully operational) to S5 (the system is completely powered OFF) and the States (S1, S2, S3 and S4) are referred to as sleeping states, in which the system appears OFF because of low power consumption and retains enough of the hardware context to return to the working state without a system reboot.

Ø      System Power State S0 the ON state: The system is completely operation, fully powered and completely retains the context.

Ø      System Power State S1 the Sleep state: The system consumes less power than S0 state. All Hardware & Processor context is maintained.

Ø      System Power State S2 the Sleep state: The system consumes less power than S1 state. Processor loses power and processor context and contents of the cache are lost.

Ø      System Power State S3 the Sleep state: The system consumes less power than S2 state. Processor & Hardware context, cache contents, and chipset context are lost. The system memory is retained.

Ø      System Power State S4 the Hibernate state: The system consumes the least power compared to all other sleep states. The system is almost at an OFF state, expect for a trickle power. The context data is written to hard drive (disk)and there is no context retained.

Ø      System Power State S5 the OFF state:The system is in a shutdown state and the system retains no context. Note that in power state S4 the system can restart from the context data stored on the disk, but in S5 the system requires a reboot.