Intel i5-2500K BX80623I52500K User Manual
Product codes
BX80623I52500K
Datasheet, Volume 1
45
Power Management
4.1.7
Interface State Combinations
4.2
Processor Core Power Management
While executing code, Enhanced Intel SpeedStep Technology optimizes the processor’s
frequency and core voltage based on workload. Each frequency and voltage operating
point is defined by ACPI as a P-state. When the processor is not executing code, it is
idle. A low-power idle state is defined by ACPI as a C-state. In general, lower power
C-states have longer entry and exit latencies.
frequency and core voltage based on workload. Each frequency and voltage operating
point is defined by ACPI as a P-state. When the processor is not executing code, it is
idle. A low-power idle state is defined by ACPI as a C-state. In general, lower power
C-states have longer entry and exit latencies.
4.2.1
Enhanced Intel
®
SpeedStep
®
Technology
The following are the key features of Enhanced Intel SpeedStep Technology:
• Multiple frequency and voltage points for optimal performance and power
efficiency. These operating points are known as P-states.
• Frequency selection is software controlled by writing to processor MSRs. The
voltage is optimized based on the selected frequency and the number of active
processor cores.
processor cores.
— If the target frequency is higher than the current frequency, V
CC
is ramped up
in steps to an optimized voltage. This voltage is signaled by the SVID bus to the
voltage regulator. Once the voltage is established, the PLL locks on to the
target frequency.
— If the target frequency is lower than the current frequency, the PLL locks to the
target frequency, then transitions to a lower voltage by signaling the target
voltage on SVID bus.
— All active processor cores share the same frequency and voltage. In a multi-
core processor, the highest frequency P-state requested amongst all active
cores is selected.
— Software-requested transitions are accepted at any time. If a previous
transition is in progress, the new transition is deferred until the previous
transition is completed.
• The processor controls voltage ramp rates internally to ensure glitch-free
transitions.
• Because there is low transition latency between P-states, a significant number of
transitions per-second are possible.
Table 4-7.
G, S and C State Combinations
Global (G)
State
Sleep
(S) State
Processor
Package
(C) State
Processor
State
System Clocks
Description
G0
S0
C0
Full On
On
Full On
G0
S0
C1/C1E
Auto-Halt
On
Auto-Halt
G0
S0
C3
Deep Sleep
On
Deep Sleep
G0
S0
C6
Deep Power-
down
On
Deep Power-down
G1
S3
Power off
Off, except RTC
Suspend to RAM
G1
S4
Power off
Off, except RTC
Suspend to Disk
G2
S5
Power off
Off, except RTC
Soft Off
G3
NA
Power off
Power off
Hard off