3-18 Software Functional Overview
Power Management Mode Definitions
A particular implementation of system power management may use some or all
of the depicted states. The following table describes the power management
states.
Power Management States
PM Mode
Mode Definition
Full-On
The system state where no devices are power managed and the
system can respond to applications with maximum performance.
Doze
The CPU clock is slowed down while all other devices are fully
operational. (Similar to IDLE mode – Transparent to the user)
Stand By (POS)
A suspend state where all motherboard components are still
powered-on except for the system clock generator device. The
PCI and CPU buses are driven to the inactive idle state. The
system memory is powered and refreshed by the memory bridge,
and the graphics frame buffer is powered and refreshed by the
graphic chip. The system provides a 32KHz clock (SUSCLK) in
this suspend mode to support the refresh function of these
memory subsystems. Only an enabled resume event can bring
the system out of the powered-on suspend (POS) state. The
PIIX4 also provides a resume timer that allows the system to
resume after a programmed time has elapsed.
Suspend to RAM (STR)
A suspend state where all motherboard components are
powered-off. The CPU/L2 and PCI busses are powered off. All
devices connected to the CPU/L2 and PCI busses must either be
powered-off or isolate their bus interfaces. The system memory
is powered and refreshed by the memory bridge, and the
graphics frame buffer is powered and refreshed by the graphics
chip. The system provides a 32 kHz clock (SUSCLK) in this
suspend mode to support refresh of these memory subsystems.
Only an enabled resume event can bring the platform out of the
suspend to RAM (STR) state.
Suspend to Disk (STD)
A suspend state where the context of the entire system is saved
to disk, all motherboard components are powered-off, and all
clocks are stopped. Any enabled “resume event”, such as
PowerBTN or RTC, can bring the platform out of the suspend to
disk (STD) state.
Soft Off (SOFF)
This is the same as suspend to disk except the context of
memory is not saved. The system will resume from Soft Off as if
a hard reset had occurred.
Mechanical Off (MOFF)
All power except the RTC has been removed from the system.
