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1.13 Power Management
Power management is implemented at several levels, including:
• Software support through Advanced Configuration and Power Interface (ACPI)
• Hardware support:
⎯ Power connector
⎯ Fan headers
⎯ LAN wake capabilities
⎯ Instantly Available PC technology
⎯ Wake from USB
⎯ Power Management Event signal (PME#) wake-up support
⎯ Wake from Consumer IR
1.13.1 ACPI
ACPI gives the operating system direct control over the power management and Plug
and Play functions of a computer. The use of ACPI with the board requires an
operating system that provides full ACPI support. ACPI features include:
• Plug and Play (including bus and device enumeration)
• Power management control of individual devices, add-in boards (some add-in
boards may require an ACPI-aware driver), video displays, and hard disk drives
• Methods for achieving less than 15-watt system operation in the power-on/standby
sleeping state
• A Soft-off feature that enables the operating system to power-off the computer
• Support for multiple wake-up events (see
Table 9 on page 33)
• Support for a front panel power and sleep mode switch
Table 7 lists the system states based on how long the power switch is pressed,
depending on how ACPI is configured with an ACPI-aware operating system.
Table 7. Effects of Pressing the Power Switch
If the system is in this
state…
…and the power switch
is pressed for
…the system enters this state
Off
(ACPI G2/G5 – Soft off)
Less than four seconds Power-on
(ACPI G0 – working state)
On
(ACPI G0 – working state)
Less than four seconds Soft-off/Standby
(ACPI G1 – sleeping state)
On
(ACPI G0 – working state)
More than four seconds Fail safe power-off
(ACPI G2/G5 – Soft off)
Sleep
(ACPI G1 – sleeping state)
Less than four seconds Wake-up
(ACPI G0 – working state)
Sleep
(ACPI G1 – sleeping state)
More than four seconds Power-off
(ACPI G2/G5 – Soft off)