Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
Legacy
Boot
(SCI_EN=0)
G3 -Mech
Off
Power
Failure/
Power Off
ACPI
Boot
(SCI_EN=1)
Modem HDD CDROM
D3 D3 D3
D2 D2 D2
D1 D1 D1
D0 D0 D0
C0
S4BIOS_F
S4BIOS_REQ
BIOS
Routine
Legacy
Legacy
Boot
(SCI_EN=0)
ACPI_ENABLE
(SCI_EN=1)
ACPI_DISABLE
(SCI_EN=0)
G2 (S5) -
Soft Off
ACPI
Boot
(SCI_EN=1)
SLP_TYPx=S5
and
SLP_EN
or
PWRBTN_OR
G0 (S0) -
Working
Performance
State Px
CPU
SLP_TYPx=(S1-S4)
and
SLP_EN
Wake
Event
Throttling
C0
C1
C2
S4
S3
S2
S1
G1 -
Sleeping
Cn
Figure 4-10 Global States and Their Transitions
The ACPI architecture defines mechanisms for hardware to generate events and control logic to
implement this behavior model. Events are used to notify OSPM that some action is needed, and
control logic is used by OSPM to cause some state transition. ACPI-defined events are “hardware”
or “interrupt” events. A hardware event is one that causes the hardware to unconditionally perform
some operation. For example, any wake event will sequence the system from a sleeping state (S1,
S2, S3, and S4 in the global G1 state) to the G0 working state (see Figure 16-76).
An interrupt event causes the execution of an event handler (AML code or an ACPI-aware driver),
which allows the software to make a policy decision based on the event. For ACPI fixed-feature
events, OSPM or an ACPI-aware driver acts as the event handler. For generic logic events OSPM
will schedule the execution of an OEM-supplied AML control method associated with the event.
For legacy systems, an event normally generates an OS-transparent interrupt, such as a System
Management Interrupt, or SMI. For ACPI systems the interrupt events need to generate an OSvisible
interrupt that is shareable; edge-style interrupts will not work. Hardware platforms that want
to support both legacy operating systems and ACPI systems support a way of re-mapping the
interrupt events between SMIs and SCIs when switching between ACPI and legacy models. This is
illustrated in the following block diagram.
64 April, 2015 Version 6.0