Low Power Features
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
While in AutoHALT Power-Down state, the processor will process bus snoops and interrupts.
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.
Since the AGTL+ signal pins receive power from the FSB, these pins should not be driven
(allowing the level to return to V
state. In addition, all other input pins on the FSB should be driven to the inactive state.
RESET# will cause the processor to immediately initialize itself, but the processor will stay in
Stop-Grant state. A transition back to the Normal state will occur with the de-assertion of the
STPCLK# signal. When re-entering the Stop-Grant state from the Sleep state, STPCLK# should be
deasserted ten or more bus clocks after the de-assertion of SLP#.
A transition to the HALT/Grant Snoop state will occur when the processor detects a snoop on the
assertion of the SLP# signal.
While in the Stop-Grant State, SMI#, INIT# and LINT[1:0] will be latched by the processor, and
only serviced when the processor returns to the Normal State. Only one occurrence of each event
will be recognized upon return to the Normal state.
While in Stop-Grant state, the processor will process snoops on the FSB and it will latch interrupts
delivered on the FSB.
The PBE# signal can be driven when the processor is in Stop-Grant state. PBE# will be asserted if
there is any pending interrupt latched within the processor. Pending interrupts that are blocked by
the EFLAGS.IF bit being clear will still cause assertion of PBE#. Assertion of PBE# indicates to
system logic that it should return the processor to the Normal state.
HALT/Grant Snoop State
The processor responds to snoop or interrupt transactions on the FSB while in Stop-Grant state or
in AutoHALT Power-Down state. During a snoop or interrupt transaction, the processor enters the
HALT/Grant Snoop state. The processor will stay in this state until the snoop on the FSB has been
serviced (whether by the processor or another agent on the FSB) or the interrupt has been latched.
After the snoop is serviced or the interrupt is latched, the processor will return to the Stop-Grant
state or AutoHALT Power-Down state, as appropriate.
2.1.3). A transition to the Sleep state (see
) for minimum power drawn by the termination resistors in this
2.1.5) will occur with the