Datasheet

Datasheet 11
Low Power Features
2 Low Power Features
2.1 Clock Control and Low Power States
The processor supports low power states both at the individual core level and the
package level for optimal power management.
A core may independently enter the C1/AutoHALT, C1/MWAIT, C2, C3, and C4 low
power states. When both cores coincide in a common core low power state, the central
power management logic ensures that the entire processor enters the respective
package low power state by initiating a P_LVLx (P_LVL2, P_LVL3, P_LVL4, or P_LVL5)
I/O read to the chipset.
The processor implements two software interfaces for requesting low power states:
MWAIT instruction extensions with sub-state hints or P_LVLx reads to the ACPI P_BLK
register block mapped in the processor’s I/O address space. The P_LVLx I/O reads are
converted to equivalent MWAIT C-state requests inside the processor and do not
directly result in I/O reads on the processor FSB. The P_LVLx I/O monitor address does
not need to be set up before using the P_LVLx I/O read interface. The sub-state hints
used for each P_LVLx read can be configured through the Model Specific Register
(MSR).
If a core encounters a chipset break event while STPCLK# is asserted, then it asserts
the PBE# output signal. Assertion of PBE# when STPCLK# is asserted indicates to
system logic that individual cores should return to the C0 state and the processor
should return to the Normal state.
Figure 1 shows the core low power states and Figure 2 shows the package low power
states. Table 1 maps the core low power states to the package low power states.