Intel i5-700, Технические характеристики

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Sensor Based Thermal Specification Design Guidance
54 Thermal/Mechanical Specifications and Design Guidelines
7.4 Fan Speed Control (FSC) design process
The next step is to incorporate the thermal solution characterization data into the
algorithms for the device controlling the fans.
As a reminder, the requirements are:
• When the DTS value is at or below T
CONTROL
, the fans can be slowed down — just
as with prior processors.
• When DTS is above T
CONTROL
, FSC algorithms will use knowledge of T
AMBIENT
and
Ψ
CA
versus RPM to achieve the necessary level of cooling.
This chapter will discuss two implementations. The first is a FSC system that is not
provided the T
AMBIENT
information and a FSC system that is provided data on the
current T
AMBIENT
. Either method will result in a thermally compliant solution and some
acoustic benefit by operating the processor closer to the thermal profile. But only the
T
AMBIENT
aware FSC system can fully use the specification for optimized acoustic
performance.
In the development of the FSC algorithm it should be noted that the T
AMBIENT
is
expected to change at a significantly slower rate than the DTS value. The DTS value will
be driven by the workload on the processor and the thermal solution will be required to
respond to this much more rapidly than the changes in T
AMBIENT
.
An additional consideration in establishing the fan speed curves is to account for the
thermal interface material performance degradation over time.
7.4.1 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 7.3.1 .
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 7-6 ). The
DTS thermal specification defines a required Ψ
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 7-6 ). The shaded area displayed in Figure 7-6 is where DTS values