Datasheet

14 Datasheet
Electrical Specifications
2.2 Clock Control and Low Power States
Pentium III processors allow the use of AutoHALT, Stop-Grant, Sleep, and Deep Sleep states to
reduce power consumption by stopping the clock to internal sections of the processor, depending
on each particular state. See Figure 3 for a visual representation of the Pentium III processor low
power states.
Figure 2. AGTL+ Bus Topology
Pentium III
Processor
Pentium III
Processor
ASIC
Figure 3. Stop Clock State Machine
PCB757
2. Auto HALT Power Down State
BCLK running.
Snoops and interrupts allowed.
HALT Instruction and
HALT Bus Cycle Generated
INIT#, BINIT#, INTR,
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
STPCLK# Asserted
STPCLK# De-asserted
and Stop-Grant State
entered from
AutoHALT
,NMI