Intel Xeon X3440 BX80605X3440 User Manual

46

Document Number: 424077 Revision: 2.0Thermal/Mechanical 

Specifications and Design Guidelines

take place. This sequence of temperature checking and Frequency/VID reduction will 
continue until either the minimum frequency has been reached or the processor 
temperature has dropped below the TCC activation point.

If the processor temperature remains above the TCC activation point even after the 
minimum frequency has been reached, then clock modulation (described below) at that 
minimum frequency will be initiated.

There is no end user software or hardware mechanism to initiate this automated TCC 
activation behavior.

A small amount of hysteresis has been included to prevent rapid active/inactive 
transitions of the TCC when the processor temperature is near the TCC activation 
temperature. Once the temperature has dropped below the trip temperature, and the 
hysteresis timer has expired, the operating frequency and voltage transition back to 
the normal system operating point using the intermediate VID/frequency points. 
Transition of the VID code will occur first, to insure proper operation as the frequency is 
increased. Refer to 

 for an illustration of this ordering.

Clock modulation is a second method of thermal control available to the processor. 

Clock modulation is performed by rapidly turning the clocks off and on at a duty cycle 

that should reduce power dissipation by about 50% (typically a 30–50% duty cycle). 

Clocks often will not be off for more than 32 microseconds when the TCC is active. 

Cycle times are independent of processor frequency. The duty cycle for the TCC, when 

activated by the Intel

®

 Thermal Monitor, is factory configured and cannot be modified.

It is possible for software to initiate clock modulation with configurable duty cycles.

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