Intel QX9775 EU80574XL088N Data Sheet

89

The processor supports Enhanced Intel SpeedStep

® 

Technology. This technology 

enables the processor to switch between multiple frequency and voltage points, which 

results in platform power savings. Enhanced Intel SpeedStep

 

Technology requires 

support for dynamic VID transitions in the platform. Switching between voltage/

frequency states is software controlled. For more configuration details also refer to the 

 64 and IA-32 Architectures Software Developer’s Manual.

Enhanced Intel SpeedStep Technology creates processor performance states (P-states) 

or voltage/frequency operating points which are lower power capability states within 

the Normal state (see 

 for the Stop Clock State Machine for supported P-

states). Enhanced Intel SpeedStep Technology enables real-time dynamic switching 

between frequency and voltage points. It alters the performance of the processor by 

changing the bus to core frequency ratio and voltage. This allows the processor to run 

at different core frequencies and voltages to best serve the performance and power 

requirements of the processor and system. The processor has hardware logic that 

coordinates the requested voltage (VID) between the processor cores. The highest 

voltage that is requested for either of the processor cores is selected for that processor 

package. Note that the front side bus is not altered; only the internal core frequency is 

changed. In order to run at reduced power consumption, the voltage is altered in step 

with the bus ratio.

The following are key features of Enhanced Intel SpeedStep Technology:

• Multiple voltage/frequency operating points provide optimal performance at 

reduced power consumption.

• Voltage/frequency selection is software controlled by writing to the processor MSR’s 

(Model Specific Registers); thus, eliminating chipset dependency.

— If the target frequency is higher than the current frequency, V

CC

 is incremented 

in steps (+12.5 mV) by placing a new value on the VID signals and the 

processor shifts to the new frequency. Note that the top frequency for the 

processor can not be exceeded.

— If the target frequency is lower than the current frequency, the processor shifts 

to the new frequency and V

CC

 is then decremented in steps (-12.5 mV) by 

changing the target VID through the VID signals.