Intel 500 - DATASHEET REV 003, Datasheet

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Datasheet 13
Low Power Features
2.1.1.3 C1/MWAIT Powerdown State
C1/MWAIT is a low-power state entered when the processor core executes the MWAIT
instruction. Processor behavior in the C1/MWAIT state is identical to the C1/AutoHALT
state except that there is an additional event that can cause the processor core to
return to the C0 state: the Monitor event. See the Intel® 64 and IA-32 Intel®
Architecture Software Developer's Manual, Volume 2A/2B: Instruction Set Reference
for more information.
2.1.1.4 Core C2 State
The core of the processor can enter the C2 state by initiating a P_LVL2 I/O read to the
P_BLK or an MWAIT(C2) instruction, but the processor does not issue a Stop Grant
Acknowledge special bus cycle unless the STPCLK# pin is also asserted.
The processor in C2 state processes only the bus snoops. The processor enters a
snoopable sub-state (not shown in Figure 2 ) to process the snoop and then return to
the C2 state.
2.1.1.5 Core C3 State
Core C3 state is a very low-power state the processor core can enter while maintaining
context. The core of the processor can enter the C3 state by initiating a P_LVL3 I/O
read to the P_BLK or an MWAIT(C3) instruction. Before entering the C3 state, the
processor core flushes the contents of its L1 cache into the processor’s L2 cache.
Except for the caches, the processor core maintains all its architectural state in the C3
state. The Monitor remains armed if it is configured. All of the clocks in the processor
core are stopped in the C3 state.
Because the core’s caches are flushed, the processor keeps the core in the C3 state
when the processor detects a snoop on the FSB. The processor core transitions to the
C0 state upon the occurrence of a Monitor event, SMI#, INIT#, LINT[1:0] (NMI, INTR),
or FSB interrupt message. RESET# causes the processor core to immediately initialize
itself.
2.1.2 Package Low-Power States
Package level low-power states are applicable to the processor.
2.1.2.1 Normal State
This is the normal operating state for the processor. The processor enters the Normal
state when the core is in the C0, C1/AutoHALT, or C1/MWAIT state.
2.1.2.2 Stop-Grant State
When the STPCLK# pin is asserted the core of the processor enters the Stop-Grant
state within 20 bus clocks after the response phase of the processor-issued Stop Grant
Acknowledge special bus cycle. When the STPCLK# pin is deasserted the core returns
to the previous core low-power state.
Since the AGTL+ signal pins receive power from the FSB, these pins should not be
driven (allowing the level to return to V
CCP
) for minimum power drawn by the
termination resistors in this state. In addition, all other input pins on the FSB should be
driven to the inactive state.
RESET# causes the processor to immediately initialize itself, but the processor stays in
Stop-Grant state. When RESET# is asserted by the system the STPCLK#, SLP#, and
DPSLP# pins must be deasserted more than 480 µs prior to RESET# deassertion (AC