Intel BX80605X3430 Data Sheet - Page 37

Enhanced Intel, SpeedStep, Technology, Low-Power Idle States

Page 37 highlights

Power Management 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. - If in the target frequency is higher than steps to an optimized voltage. This the current frequency, voltage is signaled by tVhCeCVisIDr[a7m:0p]edpiunps 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 the VID[7:0] pins. - All active processor cores share the same frequency and voltage. In a multicore 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. 4.2.2 Low-Power Idle States When the processor is idle, low-power idle states (C-states) are used to save power. More power savings actions are taken for numerically higher C-states. However, higher C-states have longer exit and entry latencies. Resolution of C-states occur at the thread, processor core, and processor package level. Thread level C-states are available if Intel Hyper-Threading Technology is enabled. Figure 4-1. Idle Power Management Breakdown of the Processor Cores Thread 0 Thread 1 Thread 0 Thread 1 Core 0 State Core 1 State Processor Package State Datasheet, Volume 1 37

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Datasheet, Volume 1
37
Power Management
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.
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 VID[7:0] pins
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 the VID[7:0] pins.
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.
4.2.2
Low-Power Idle States
When the processor is idle, low-power idle states (C-states) are used to save power.
More power savings actions are taken for numerically higher C-states. However, higher
C-states have longer exit and entry latencies. Resolution of C-states occur at the
thread, processor core, and processor package level. Thread level C-states are
available if Intel Hyper-Threading Technology is enabled.
Figure 4-1.
Idle Power Management Breakdown of the Processor Cores
Processor Package State
Core 1 State
Thread 1
Thread 0
Core 0 State
Thread 1
Thread 0