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

Legacy Fan Speed Control
116 Thermal and Mechanical Design Guidelines
The BIOS, at a minimum, must program the settings in Table 14 or Table 15, as
appropriate, into the fan speed controller. The values are the minimum required to
establish a fan speed control algorithm consistent with this document, the reference
thermal solution, and Boxed processor thermal solution.
Table 14. ATX FSC Settings
Parameter Classification Processor Thermal
Sensor
PWM Output Notes
T
HIGH
Required T
CONTROL
3
T
LOW
Required T
CONTROL
– 10 °C 3
Minimum PWM
Duty Cycle
Required 20%
PWM Frequency Required 21–28 kHz 1
Spin-up time Suggested 250 - ~500 ms 2,4
T
AVERAGING
Suggested 35 sec 6
When T
SENSOR
<
T
LOW
Suggested Minimum PWM%
All Fans ON Suggested T
CONTROL
+ 3 °C
Hysteresis Suggested 2 °C
NOTE:
1. A PWM frequency of 25 kHz is the design target for the reference and for the Intel
®
Boxed processor and the reference design.
2. Use the lowest time available in this range for the device selected.
3. To ensure compliance with the thermal specification, thermal profile and usage of the
TSENSOR for fan speed control these setting should not be user configurable.
4. If this function is present on the device it must be enabled