Intel Z520PT CH80566EE014DT Data Sheet
Product codes
CH80566EE014DT
Low Power Features
Datasheet
13
2
Low Power Features
2.1
Clock Control and Low-Power States
The processor supports low power states at the thread level and the core/package
level. Thread states (TCx) loosely correspond to ACPI processor power states (Cx). A
thread may independently enter the TC1/AutoHALT, TC1/MWAIT, TC2, TC4, or TC6
low power states, but this does not always cause a power state transition. Only when
both threads request a low-power state (TCx) greater than the current processor state
will a transition occur. The central power management logic ensures the entire
processor enters the new common processor power state. For processor power states
higher than C1, this would be done by initiating a P_LVLx (P_LVL2 and P_LVL3) I/O
read to the chipset by both threads. Package states are states that require external
intervention and typically map back to processor power states. Package states for the
processor include Normal (C0, C1), Stop Grant and Stop Grant Snoop (C2), Deeper
Sleep (C4), and Deep Power Down Technology (C6).
The processor implements two software interfaces for requesting low power states:
MWAIT instruction extensions with sub-state hints and 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 monitor address does not
need to be setup before using the P_LVLx I/O read interface. The sub-state hints used
for each P_LVLx read can be configured in a software programmable MSR by BIOS. If
a thread 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 threads should return to the C0 state and the processor
should return to the Normal state.
states. Table 2 provides a mapping of thread low-power states to package low power
states.