Intel Pentium 4 Processor in the 478-PinPackage at 1.40 GHz, 1.50 GHz, 1.60 GHz, 1.70 GHz, 1.80 GHz, 1.90 GHz, and 2GHz

Features
82 Datasheet
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 deasserts the STPCLK# interrupt, the processor will return
execution to the HALT state.
While in AutoHALT Power Down state, the processor will process bus snoops.
7.2.3 Stop-Grant State—State 3
When the STPCLK# pin is asserted, the Stop-Grant state of the processor is entered 20
bus clocks after the response phase of the processor-issued Stop Grant Acknowledge
special bus cycle. Once the STPCLK# pin has been asserted, it may only be deasserted
once the processor is in the Stop Grant state.
Figure 31. Stop Clock State Machine
2. Auto HALT Power Down State
BCLK running.
Snoops and interrupts allowed.
HALT Instruction and
HALT Bus Cycle Generated
INIT#, BINIT#, INTR, NMI,
SMI#, RESET#
1. Normal State
Normal execution.
STPCLK#
Asserted
STPCLK#
De-asserted
3. Stop Grant State
BCLK running.
Snoops and interrupts allowed.
SLP#
Asserted
SLP#
De-asserted
5. Sleep State
BCLK running.
No snoops or interrupts allowed.
BCLK
Input
Stopped
BCLK
Input
Restarted
6. Deep Sleep State
BCLK stopped.
No snoops or interrupts allowed.
4. HALT/Grant Snoop State
BCLK running.
Service snoops to caches.
Snoop Event Occurs
Snoop Event Serviced
Snoop
Event
Occurs
Snoop
Event
Serviced
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