Acoustic Fan Speed Control
R
Thermal/Mechanical Design Guide
53
6
Acoustic Fan Speed Control
6.1
Acoustic Fan Speed Control
As processor power has increased, the required thermal solutions have generated increasingly
more noise. Intel has added an option to the processor thermal specifications that allows the
system integrators to have a quieter system under typical usage. T
CONTROL
and the on-die thermal
diode provide the system integrator the means to implement a quieter system design.
Acoustic fan control implementations consist of the following items
•
A motherboard designed with a fan speed controller with the following functionality:
⎯
PWM fan control output
⎯
Remote thermal diode measurement capability
•
A motherboard with a 4-pin fan header for the processor heatsink fan.
•
Processor heatsink with 4–wire PWM controlled Fan.
A thermistor in the fan hub is recommended, but not a requirement. The reference solution
and the Boxed Pentium 4 Processor in 775–land LGA package have implemented a
thermistor into the design.
The following sections will discuss the necessary steps to implement Acoustic Fan Speed Control.
6.2
Thermal Solution Design
6.2.1
Compliance to Thermal Profile
The first step is to select or design a processor thermal solution that meets the thermal profile for
the Pentium 4 Processor in the 775–land LGA Package. See Section 2.2.2 for the definition of the
thermal profile then consult the processor datasheet.
The designer needs to ensure that when the heat sink fan is operating at full speed the thermal
solution will meet the T
C-MAX
limits at TDP. The slope of the thermal profile allows the designer
to make tradeoffs in thermal performance versus the inlet temperature to the processor fan
heatsink.
6.2.2
Determine Thermistor Set Points
A thermistor implemented in the hub of a fan is a first level of fan speed control. It provides an
easy and cost effective means to begin acoustic noise reduction. It will, by design, run the fan at
an appropriate speed based on the ambient conditions.
Summary of Contents for 640 - Pentium 4 640 3.2GHz 800MHz 2MB Socket 775 CPU
Page 14: ...Introduction R 14 Thermal Mechanical Design Guide ...
Page 38: ...Thermal Management Logic and Thermal Monitor Feature R 38 Thermal Mechanical Design Guide ...
Page 52: ...Intel Thermal Mechanical Reference Design Information R 52 Thermal Mechanical Design Guide ...
Page 60: ...Acoustic Fan Speed Control R 60 Thermal Mechanical Design Guide ...
Page 72: ...Heatsink Clip Load Metrology R 72 Thermal Mechanical Design Guide ...
Page 99: ...Mechanical Drawings R Thermal Mechanical Design Guide 99 Figure 50 Reference Fastener Sheet 1 ...
Page 103: ...Mechanical Drawings R Thermal Mechanical Design Guide 103 Figure 54 Clip Heatsink Assembly ...