Intel 2ND GENERATION CORE PROCESSOR FAMILY DESKTOP - THERMAL MECHANICAL S AND DESIGN GUIDELINES 01-2011, Технические характеристики

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Sensor Based Thermal Specification Design Guidance
70 Thermal/Mechanical Specifications and Design Guidelines
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
AMBIENT
Data
In a system that does not provide the FSC algorithm with the T
AMBIENT
information, the
designer must make the following assumption:
• When the DTS value is greater than T
CONTROL
, the T
AMBIENT
is at boundary condition
derived in Section 8.3.1 .
This is consistent past FSC guidance from Intel, to accelerate the fan to full speed when
the DTS value is greater than T
CONTROL
. As will be shown below, the DTS thermal
specification at DTS = T
CONTROL
can reduce some of the over cooling of the processor
and provide an acoustic noise reduction from the processor thermal solution.
In this example the following assumptions are made:
• T
AMBIENT
= 40 °C
• Thermal Solution designed / validated to a 40 °C environment
• T
CONTROL
= -20
• Reference processor thermal solution (RCFH7-1156 (DHA-A))
• Below T
CONTROL
the fan speed is slowed down as in prior products
For a processor specification based on a T
CASE
thermal profile, when the DTS value is
equal to or greater than T
CONTROL
, the fan speed must be accelerated to full speed. For
the reference thermal solution, full speed is 3150 RPM (dashed line in Figure 8-6 ). The
DTS thermal specification defines a required 
CA
at T
CONTROL
and the fan speed is 2300
RPM. This is much less than full speed even when assuming the T
AMBIENT
= 40 °C (solid
line in Figure 8-6 ). The shaded area displayed in Figure 8-6 is where DTS values are
less than T
CONTROL
. For simplicity, the graph shows a linear acceleration of the fans
from
T
CONTROL
- 10 to T
CONTROL
as has been Intel’s guidance for simple fan speed 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.