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Appendix E Board Level PWM and Fan Speed
Control Requirements
To utilize all of the features in the Intel reference heatsink design or the Intel boxed processor
design, system integrators should verify the following functionality is present in the board design.
Please refer to the Fan Specification for 4-Wire PWM Controlled Fans.
Requirements Classification:
•
Required – an essential part of the design necessary to meet specifications. Should be
considered a pass or fail in selection of a board.
•
Recommended – necessary for consistency among designs. May be specified or expanded by
the system integrator.
The motherboard needs to have a fan speed control component that has the following
characteristics
•
PWM output of 21-28 KHz (required).
•
PWM output set to 25 KHz (recommended) this value is the design target for the reference and
for the Intel boxed processor solutions.
•
Has external/remote thermal diode measurement capability (required).
•
External/remote thermal diode sampling rate = 4 times per second (required).
•
External/remote diode measurement is calibrated by the component vendor to account for the
diode ideality and package series resistance as listed in the appropriate datasheet.
(recommended).
Note: If the fan speed controller is not calibrated with the diode ideality and package series resistance,
verify the board manufacturer has made provisions within the BIOS setup or other utility to input
the corrections factors.
The BIOS must be enabled to program the following data into the fan speed controller.
•
Turns on PWM functionality within the required frequency range (required).
•
Has the minimum and maximum values for the fan speed (RPM) ramp (required).
•
Has minimum temperature where the fan speed will begin ramping. (required).
•
Has maximum temperature used for the fan speed (RPM) ramp set equal to T
(required).
Note: The fan speed component vendors provide libraries that are used by the BIOS writer to program the
component registers with the parameters listed above. Consult the appropriate vendor datasheet for
detailed information on programming their component.
®
®
Intel
Celeron
D Processor in the 775-Land LGA Package Thermal Design Guide57
303730
Order #
Board Level PWM and Fan Speed Control Requirements
CONTROL
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