Intel QX9770 Design Guidelines - Page 104
Table 12. FSC Definitions, Fan Specification for 4 wire PWM Controlled Fans
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Legacy Fan Speed Control To use all of the features in the Intel reference heatsink design or the Boxed Processor, system integrators should verify the following functionality is present in the board design. Refer to the Fan Specification for 4 wire PWM Controlled Fans and Chapter 5 for complete details on the Intel enabled thermal solution. The FSC definitions are listed in Table 12. Table 12. FSC Definitions Item Definition TSENSOR TCONTROL TLOW Hysteresis THIGH All Fans ON Min PWM Spin-up PWM Freq TAVERAGING Temperature reported from the processor digital thermal sensor. TCONTROL is the specification limit for use with the digital thermal sensor The temperature above which the fan will begin to accelerate in response to the digital thermal sensor temperature. The number of degrees below TCONTROL the fans will remain on before slowing down. The temperature at which the fan is operating at full speed (100% PWM Duty Cycle). By specification this is Tcontrol. The processor temperature at which all fans in the system are increased to 100% Duty Cycle. Minimum pulse width modulation (% duty cycle) that the fans will run at when TSENSOR is less than TLOW. Amount of time fan is run at 100% duty cycle to overcome fan inertia. The operating frequency of the PWM signal. The time (in seconds) that elapses while the fan is gradually sped up in response to a processor temperature spike. 104 Thermal and Mechanical Design Guidelines