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Description 29
Table 5 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 5. 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)
System States and Power States
Under ACPI, the operating system directs all system and device power state transitions. The
operating system puts devices in and out of low-power states based on user preferences and
knowledge of how devices are being used by applications. Devices that are not being used can be
turned off. The operating system uses information from applications and user settings to put the
system as a whole into a low-power state.
Table 6 lists the power states supported by the S845WD1-E board along with the associated system
power targets. See the ACPI specification for a complete description of the various system and
power states.
Table 6. Power States and Targeted System Power
Global States
Sleeping States
Processor
States
Device States
Targeted System
Power
(Note 1)
G0 – working
state
S0 – working C0 – working D0 – working
state.
Full power > 30 W
G1 – sleeping
state
S1 – Processor
stopped
C1 – stop
grant
D1, D2, D3 –
device
specification
specific.
5 W < power < 52.5 W
G1 – sleeping
state
S3 – Suspend to
RAM. Context
saved to RAM.
No power D3 – no power
except for
wake-up logic.
Power < 5 W
(Note 2)
G1 – sleeping
state
S4 – Suspend to
disk. Context
saved to disk.
No power D3 – no power
except for
wake-up logic.
Power < 5 W
(Note 2)
continued