Datasheet
Features
88 Datasheet
6.2.1 Normal State
This is the normal operating state for the processor.
6.2.2 HALT and Extended HALT Powerdown States
The processor supports the HALT or Extended HALT powerdown state. The Extended
HALT powerdown state must be configured and enabled using the BIOS for the
processor to remain within specification.
The Extended HALT state is a lower power state as compared to the Stop Grant State.
If Extended HALT is not enabled, the default powerdown state entered will be HALT.
Refer to the sections below for details about the HALT and Extended HALT states.
6.2.2.1 HALT Powerdown State
HALT is a low power state entered when all the processor cores have executed the HALT
or MWAIT instructions. When one of the processor cores executes the HALT instruction,
that processor core is halted, however, the other processor continues normal operation.
The halted core will transition to the Normal state upon the occurrence of SMI#, INIT#,
or LINT[1:0] (NMI, INTR). RESET# will cause the processor to immediately initialize
itself.
Figure 19. Processor Low Power State Machine
Normal State
- Normal Execution
Stop Grant State
- BCLK running
- Snoops and interrupts
allowed
Extended Stop Grant or
Stop Grant Snoop State
- BCLK running
- Service Snoops to caches
Extended HALT Snoop or
HALT Snoop State
- BCLK running
- Service Snoops to caches
Extended HALT or HALT
State
- BCLK running
- Snoops and interrupts
allowed
HALT or MWAIT Instruction and
HALT Bus Cycle Generated
INIT#, INTR, NMI, SMI#, RESET#,
FSB interrupts
STPCLK#
Asserted
STPCLK#
De-asserted
STPCLK#
Asserted
STPCLK#
De-asserted
Snoop
Event
Occurs
Snoop
Event
Serviced
Snoop Event Occurs
Snoop Event Serviced
Sleep State
- BCLK running
- No Snoops or
interrupts allowed
- PECI unavailable in
this state
Deep Sleep State
- BCLK can be stopped
- No Snoops or
interrupts allowed
- PECI unavailable in
this state
Deeper Sleep State
- BCLK can be stopped
- No Snoops or
interrupts allowed
- PECI unavailable in
this state
SLP#
Asserted
SLP#
De-asserted
DPSLP#
Asserted
DPSLP#
De-asserted
DPRSTP#
Asserted
DPRSTP#
De-asserted