Fan Speed Control Algorithm Without Tambient Data - Intel 2ND GENERATION CORE PROCESSOR FAMILY DESKTOP - THERMAL MECHANICAL SPECIFICATIONS AND DESIGN GUIDELINES 01-2011 Specifications

An additional consideration in establishing the fan speed curves is to account for the
thermal interface material performance degradation over time.
8.4.1 Fan Speed Control Algorithm without T
In a system that does not provide the FSC algorithm with the T
designer must make the following assumption:
• When the DTS value is greater than T
derived in
This is consistent past FSC guidance from Intel, to accelerate the fan to full speed when
the DTS value is greater than T
specification at DTS = T
and provide an acoustic noise reduction from the processor thermal solution.
In this example the following assumptions are made:
• T
AMBIENT
• Thermal Solution designed / validated to a 40 °C environment
• T
CONTROL
• Reference processor thermal solution (RCFH7-1156 (DHA-A))
• Below T
For a processor specification based on a T
equal to or greater than T
the reference thermal solution, full speed is 3150 RPM (dashed line in
DTS thermal specification defines a required 
RPM. This is much less than full speed even when assuming the T
line in Figure
less than T
from
T
CONTROL
algorithms.
As the processor workload continues to increase, the DTS value will increase and the
FSC algorithm will linearly increase the fan speed from the 2300 RPM at DTS = -20 to
full speed at DTS value = -1.
70
Section 8.3.1.
CONTROL
can reduce some of the over cooling of the processor
CONTROL
= 40 °C
= -20
the fan speed is slowed down as in prior products
CONTROL
CONTROL
8-6). The shaded area displayed in
. For simplicity, the graph shows a linear acceleration of the fans
CONTROL
- 10 to T as has been Intel's guidance for simple fan speed control
CONTROL
Sensor Based Thermal Specification Design Guidance
, the T
CONTROL AMBIENT
. As will be shown below, the DTS thermal
thermal profile, when the DTS value is
CASE
, the fan speed must be accelerated to full speed. For
at T
CA CONTROL
Figure 8-6
Thermal/Mechanical Specifications and Design Guidelines
Data
AMBIENT
information, the
AMBIENT
is at boundary condition
Figure 8-6). The
and the fan speed is 2300
= 40 °C (solid
AMBIENT
is where DTS values are