Intel Core2 Duo Desktop Processor, Intel Pentium Processor, and Intel Pentium 4 Processor 6x1 Sequence

Legacy Fan Speed Control
Thermal and Mechanical Design Guidelines 117
Table 15. Balanced Technology Extended (BTX) Fan Speed Control Settings
Parameter Classification Processor
Thermal
Sensor
System
Ambient
Sensor
PWM Output Notes
T
HIGH
Required T
CONTROL
54 °C 3,5
T
LOW
Required T
CONTROL
– 7 °C 47 °C 3,5
Minimum PWM Duty
Cycle
Required PWM 1 (TMA) –20%
PWM Frequency Required 21–28 kHz 1
Spin Up Time Suggested 250 - ~ 500 ms 2, 7
T
AVERAGING
Suggested 4.0 sec 4.0 sec 3, 7
When T
SENSOR
< T
LOW
Suggested Minimum
PWM%
Minimum
PWM%
All Fans On Suggested T
CONTROL
+ 3 °C 65 °C
Hysteresis Suggested 2 °C 4 °C
NOTE:
5. A PWM frequency of 25 kHz is the design target for the reference and for the Intel Boxed
processor and the reference design.
6. Use the lowest time available in this range for the device selected
7. T
AVERAGING
= represents the amount of delay time before responding to the temperature
change, defined in fan speed control device (sometimes called ramp range control or spike
smoothing). Select the lowest setting available close to 4.0 seconds by the fan speed
control device
8. The Fan Speed Controller, or Health Monitor Component, takes the result of the two fan
speed ramps (processor and system) and drives the TMA fan to the highest resulting PWM
duty cycle (%)
9. For BTX systems a second thermal sensor is recommended to capture chassis ambient for
more detail see
Appendix F.
10. To ensure compliance with the thermal specification, thermal profile, and usage of the
T
SENSOR
for fan speed control these setting should not be user configurable.
11. If this function is present on the device it must be enabled.
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.
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