Intel PentiumD 950 HH80553PG0964M User Manual

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This is the normal operating state for the processor.

The processor supports the HALT or Enhanced HALT powerdown state. The Enhanced 

HALT Powerdown state is configured and enabled via the BIOS. The Enhanced HALT 

specifications. 

The Enhanced HALT state is a lower power state as compared to the Stop Grant State.

HALT is a low power state entered when all the logical processors have executed the 

HALT or MWAIT instructions. When one of the logical processors executes the HALT 

instruction, that logical processor is halted; however, the other processor continues 

normal operation. 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 HALT Power Down state. See the Intel Architecture Software 

Developer's Manual, Volume III: System Programmer's Guide for more information.

BCLK running
Snoops and interrupts allowed

Normal execution

BCLK running
Service snoops to caches

BCLK running
Snoops and interrupts allowed

Snoop

Event

Occurs

Snoop

Event

Serviced

INIT#, BINIT#, INTR, NMI, SMI#,
RESET#, FSB interrupts

STPCLK#
Asserted

STPCLK#
De-asserted

S

TPCL

K

#

Asse

rted

STP

CL

K

#

D

e-

asse

rte

d

Snoop Event Occurs

Snoop Event Serviced

HALT or MWAIT Instruction and
HALT Bus Cycle Generated

BCLK running
Service snoops to caches