Intel P8700 Data Sheet - Page 14

Core C1/MWAIT Powerdown State, Core C2 State

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Low Power Features 2.1.1.3 2.1.1.4 2.1.1.5 2.1.1.6 The system can generate a STPCLK# while the processor is in the AutoHALT Powerdown state. When the system deasserts the STPCLK# interrupt, the processor will return execution to the HALT state. While in AutoHALT Powerdown state, the dual-core processor will process bus snoops and snoops from the other core. The processor core will enter a snoopable sub-state (not shown in Figure 1) to process the snoop and then return to the AutoHALT Powerdown state. Core C1/MWAIT Powerdown State C1/MWAIT is a low-power state entered when the processor core executes the MWAIT(C1) instruction. Processor behavior in the MWAIT state is identical to the AutoHALT state except that Monitor events can cause the processor core to return to the C0 state. See the Intel® 64 and IA-32 Architectures Software Developer's Manuals, Volume 2A: Instruction Set Reference, A-M and Volume 2B: Instruction Set Reference, N-Z, for more information. Core C2 State Individual cores of the dual-core 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 will not issue a Stop-Grant Acknowledge special bus cycle unless the STPCLK# pin is also asserted. While in the C2 state, the dual-core processor will process bus snoops and snoops from the other core. The processor core will enter a snoopable sub-state (not shown in Figure 1) to process the snoop and then return to the C2 state. Core C3 State Individual cores of the dual-core 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 C3, the processor core flushes the contents of its L1 caches into the processor's L2 cache. Except for the caches, the processor core maintains all its architectural states 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 or when the other core of the dual-core processor accesses cacheable memory. The processor core will transition to the C0 state upon occurrence of a Monitor event, SMI#, INIT#, LINT[1:0] (NMI, INTR), or FSB interrupt message. RESET# will cause the processor core to immediately initialize itself. Core C4 State Individual cores of the dual-core processor can enter the C4 state by initiating a P_LVL4 or P_LVL5 I/O read to the P_BLK or an MWAIT(C4) instruction. The processor core behavior in the C4 state is nearly identical to the behavior in the C3 state. The only difference is that if both processor cores are in C4, the central power management logic will request that the entire processor enter the Deeper Sleep package low-power state (see Section 2.1.2.6). To enable the package-level Intel Enhanced Deeper Sleep state, Dynamic Cache Sizing and Intel Enhanced Deeper Sleep state fields must be configured in the PMG_CST_CONFIG_CONTROL MSR. Refer to Section 2.1.2.6 for further details on Intel Enhanced Deeper Sleep state. 14 Datasheet

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Low Power Features
14
Datasheet
The system can generate a STPCLK# while the processor is in the AutoHALT
Powerdown state. When the system deasserts the STPCLK# interrupt, the processor
will return execution to the HALT state.
While in AutoHALT Powerdown state, the dual-core processor will process bus snoops
and snoops from the other core. The processor core will enter a snoopable sub-state
(not shown in
Figure 1
) to process the snoop and then return to the AutoHALT
Powerdown state.
2.1.1.3
Core C1/MWAIT Powerdown State
C1/MWAIT is a low-power state entered when the processor core executes the
MWAIT(C1) instruction. Processor behavior in the MWAIT state is identical to the
AutoHALT state except that Monitor events can cause the processor core to return to
the C0 state. See the
Intel® 64 and IA-32 Architectures Software Developer's Manuals,
Volume 2A: Instruction Set Reference, A-M
and
Volume 2B: Instruction Set Reference,
N-Z
, for more information.
2.1.1.4
Core C2 State
Individual cores of the dual-core 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 will not issue a
Stop-Grant Acknowledge special bus cycle unless the STPCLK# pin is also asserted.
While in the C2 state, the dual-core processor will process bus snoops and snoops from
the other core. The processor core will enter a snoopable sub-state (not shown in
Figure 1
) to process the snoop and then return to the C2 state.
2.1.1.5
Core C3 State
Individual cores of the dual-core 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 C3, the processor
core flushes the contents of its L1 caches into the processor’s L2 cache. Except for the
caches, the processor core maintains all its architectural states 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 or when the other core of the dual-core
processor accesses cacheable memory. The processor core will transition to the C0
state upon occurrence of a Monitor event, SMI#, INIT#, LINT[1:0] (NMI, INTR), or FSB
interrupt message. RESET# will cause the processor core to immediately initialize itself.
2.1.1.6
Core C4 State
Individual cores of the dual-core processor can enter the C4 state by initiating a P_LVL4
or P_LVL5 I/O read to the P_BLK or an MWAIT(C4) instruction. The processor core
behavior in the C4 state is nearly identical to the behavior in the C3 state. The only
difference is that if both processor cores are in C4, the central power management logic
will request that the entire processor enter the Deeper Sleep package low-power state
(see
Section 2.1.2.6
).
To enable the package-level Intel Enhanced Deeper Sleep state, Dynamic Cache Sizing
and Intel Enhanced Deeper Sleep state fields must be configured in the
PMG_CST_CONFIG_CONTROL MSR. Refer to
Section 2.1.2.6
for further details on Intel
Enhanced Deeper Sleep state.