Just as Windows Plug and Play features require support from a system’s hardware, its power-management capabilities require hardware that complies with the Advanced Configuration and Power Interface (ACPI) specification (available at http://www.acpi.info).
The ACPI standard defines various power levels for a system and for devices. The six system power states are described in Table 8-8. They are referred to as S0 (fully on or working) through S5 (fully off). Each state has the following characteristics:
Power consumption The amount of power the computer consumes
Software resumption The software state from which the computer resumes when moving to a “more on” state
Hardware latency The length of time it takes to return the computer ...