Intel Pga478 Data Sheet - Page 11

Core Low Power States

Page 11 highlights

Low Power Features-Intel® Celeron® Processor 1.66 GHz/1.83 GHz Figure 2. Core Low Power States C1/ MWAIT STPCLK# asserted STPCLK# de-asserted Stop Grant STPCLK# de-asserted STPCLK# asserted STPCLK# asserted Core state break or MONITOR STPCLK# de-asserted HLT instruction MWAIT(C1) Halt break C1/Auto Halt C0 2.1.1 2.1.1.1 2.1.1.2 halt break = A20M#transition, INIT#, INTR, NMI, PREQ#, RESET#, SMI#, or APIC interrupt core state break = (halt break OR MONITOR event) AND STPCLK# high (not asserted) Core Low Power States C0 State - Normal State This is the normal operating state for the processor. C1/AutoHALT Powerdown State AutoHALT is a low power state entered when the processor executes the HALT instruction. The processor transitions to the Normal state upon the occurrence of SMI#, BINIT#, INIT#, LINT[1:0] (NMI, INTR), or an interrupt delivered over the system bus. RESET# causes 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. Refer to the Intel® 64 and IA-32 Architectures Software Developer's Manuals in Volume 3A/3B: System Programming Guide for more information. The system can generate a STPCLK# while the processor is in the AutoHALT Power Down state. When the system deasserts the STPCLK# interrupt, the processor returns execution to the HALT state. While in AutoHALT Power Down state, the processor continues to processes system bus snoops. January 2007 Order Number: 315876-002 Intel® Celeron® Processor 1.66 GHz/1.83 GHz DS 11

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Intel
®
Celeron
®
Processor 1.66 GHz/1.83 GHz
January 2007
DS
Order Number: 315876-002
11
Low Power Features—Intel
®
Celeron
®
Processor 1.66 GHz/1.83 GHz
2.1.1
Core Low Power States
2.1.1.1
C0 State - Normal State
This is the normal operating state for the processor.
2.1.1.2
C1/AutoHALT Powerdown State
AutoHALT is a low power state entered when the processor executes the HALT
instruction. The processor transitions to the Normal state upon the occurrence of SMI#,
BINIT#, INIT#, LINT[1:0] (NMI, INTR), or an interrupt delivered over the system bus.
RESET# causes 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. Refer to the
Intel® 64 and IA-32
Architectures Software Developer's Manuals
in
Volume 3A/3B: System Programming
Guide
for more information.
The system can generate a STPCLK# while the processor is in the AutoHALT Power
Down state. When the system deasserts the STPCLK# interrupt, the processor returns
execution to the HALT state.
While in AutoHALT Power Down state, the processor continues to processes system bus
snoops.
Figure 2.
Core Low Power States
Stop
Grant
C1/Auto
Halt
C0
C1/
MWAIT
halt break = A20M#transition, INIT#, INTR, NMI, PREQ#, RESET#, SMI#, or APIC interrupt
core state break = (halt break OR MONITOR event) AND STPCLK# high (not asserted)
Halt break
HLT instruction
MWAIT(C1)
Core state break
or MONITOR
STPCLK#
de-asserted
STPCLK#
asserted
STPCLK#
de-asserted
STPCLK#
asserted
STPCLK#
asserted
STPCLK#
de-asserted