Intel i3-4360T CM8064601481958 User Manual

Product codes
CM8064601481958
Page of 125
Figure 13.
Thread and Core C-State Entry and Exit
C1
C1E
C7
C6
C3
C0
MWAIT(C1), HLT
C0
MWAIT(C7),
P_LVL4 I/O Read
MWAIT(C6),
P_LVL3 I/O Read
MWAIT(C3),
P_LVL2 I/O Read
MWAIT(C1), HLT
(C1E Enabled)
While individual threads can request low-power C-states, power saving actions only
take place once the core C-state is resolved. Core C-states are automatically resolved
by the processor. For thread and core C-states, a transition to and from C0 is required
before entering any other C-state.
Table 18.
Coordination of Thread Power States at the Core Level
Processor Core C-State
Thread 1
C0
C1
C3
C6
C7
Thread 0
C0
C0
C0
C0
C0
C0
C1
C0
C1
1
C1
1
C1
1
C1
1
C3
C0
C1
1
C3
C3
C3
C6
C0
C1
1
C3
C6
C6
C7
C0
C1
1
C3
C6
C7
Note: 1. If enabled, the core C-state will be C1E if all cores have resolved a core C1 state or higher.
Requesting Low-Power Idle States
The primary software interfaces for requesting low-power idle states are through the
MWAIT instruction with sub-state hints and the HLT instruction (for C1 and C1E).
However, software may make C-state requests using the legacy method of I/O reads
from the ACPI-defined processor clock control registers, referred to as P_LVLx. This
method of requesting C-states provides legacy support for operating systems that
initiate C-state transitions using I/O reads.
For legacy operating systems, P_LVLx I/O reads are converted within the processor to
the equivalent MWAIT C-state request. Therefore, P_LVLx reads do not directly result
in I/O reads to the system. The feature, known as I/O MWAIT redirection, must be
enabled in the BIOS.
The BIOS can write to the C-state range field of the PMG_IO_CAPTURE MSR to restrict
the range of I/O addresses that are trapped and emulate MWAIT like functionality.
Any P_LVLx reads outside of this range do not cause an I/O redirection to MWAIT(Cx)
like request. The reads fall through like a normal I/O instruction.
4.2.3  
Power Management—Processor
Desktop 4th Generation Intel
®
 Core
 Processor Family, Desktop Intel
®
 Pentium
®
 Processor Family, and Desktop Intel
®
 Celeron
®
Processor Family
July 2014
Datasheet – Volume 1 of 2
Order No.: 328897-009
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