Board And System Implementation; Choosing Fan Speed Control Settings; Figure 58. Example Fan Speed Control Implementation - Intel QX9770 - Core 2 Extreme Quad-Core Processor Design Manual

Legacy Fan Speed Control
E.2

Board and System Implementation

Once the thermal solution is defined, the system designer and board designer can
define the fan speed control implementation. The first step is to select the
appropriate fan speed controller (FSC). Figure 58 shows the major connections for a
typical implementation.

Figure 58. Example Fan Speed Control Implementation

A number of major manufacturers have FSC components that include the necessary
functionality to measure the temperature of the digital thermal sensor via the PECI
interface and output a PWM signal. These components can be a discrete device or a
super IO (SIO) with the functionality embedded. Intel has engaged with a number of
major manufacturers of FSC components to provide devices that have a PECI host
controller. Please contact your Intel Field Sales representative for the current list of
manufacturers and visit their web sites or contact your local sales representatives for
a part suitable for your design.
E.2.1

Choosing Fan Speed Control Settings

Fan speed control algorithms allow the system thermal engineer a number of options
to consider. The typical control settings that need to be considered are:
• The temperature when the fan will begin to accelerate in response to the digital
thermal sensor temperature (T
• The temperature where the fan is operating at full speed (100% PWM duty cycle).
By specification this is T
• The minimum fan speed (PWM duty cycle). For any digital thermal sensor
temperature less than T
Thermal and Mechanical Design Guidelines
)
LOW
.
CONTROL
the fan will run at this speed
LOW
99