Features
6.2.2
AutoHALT Powerdown State—State 2
AutoHALT is a low power state entered when the processor executes the HALT instruction. The
processor will transition to the Normal state upon the occurrence of SMI#, BINIT#, INIT#, or
LINT[1:0] (NMI, INTR). RESET# will cause the processor to immediately initialize itself.
The return from a System Management Interrupt (SMI) handler can be to either Normal Mode or
the AutoHALT Power Down state. See the Intel Architecture Software Developer's Manual,
Volume III: System Programmer's Guide for more information.
The system can generate a STPCLK# while the processor is in the AutoHALT Power Down state.
When the system de-asserts the STPCLK# interrupt, the processor will return execution to the
HALT state.
While in AutoHALT Power Down state, the processor will process FSB snoops and interrupts.
Figure 6-1. Stop Clock State Machine
HALT Instruction and
HALT Bus Cycle Generated
2. Auto HALT Power Down State
BCLK running.
Snoops and interrupts allowed.
1. Normal State
Normal execution.
INIT#, BINIT#, INTR, NMI,
SMI#, RESET#
Snoop
Event
Occurs
Snoop
Event
Serviced
STPCLK#
Asserted
STPCLK#
De-asserted
3. Stop Grant State
BCLK running.
Snoops and interrupts allowed.
4. HALT/Grant Snoop State
BCLK running.
Service snoops to caches.
Snoop Event Occurs
Snoop Event Serviced
SLP#
SLP#
Asserted
De-asserted
5. Sleep State
BCLK running.
No snoops or interrupts allowed.
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Datasheet
INTEL [ INTEL ]
