Intel i5-2390T CM8062301002115 User Manual

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Datasheet, Volume 1

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.

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 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.