Product Description
35
1.12.1.1 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 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)
G2/S5
S5 – Soft off.
Context not saved.
Cold boot is
required.
No power
D3 – no power
except for wake-up
logic.
Power < 5 W
(Note 2)
G3 –
mechanical off
AC power is
disconnected
from the
computer.
No power to the
system.
No power
D3 – no power for
wake-up logic,
except when
provided by battery
or external source.
No power to the system.
Service can be
performed safely.
Notes:
1.
Total system power is dependent on the system configuration, including add-in boards and peripherals powered
by the system chassis’ power supply.
2.
Dependent on the standby power consumption of wake-up devices used in the system.
1.12.1.2 One-Watt
Standby
In 2001, the U.S. government issued an executive order requiring a reduction in power for
appliances and personal computers. This board meets that requirement by operating at 1 W (or
less) in S5 (Standby) mode. One-Watt operation applies only to the S5 state when the computer is
turned off, but still connected to AC power. One-Watt operation does not apply to the S3 (Suspend
to RAM) or S4 (Suspend to disk) states.
Newer energy-efficient power supplies using less than 0.5 W (in Standby mode) may also be
needed to achieve this goal.
