Guide

28 Intel
®
Celeron
®
D Processor for Embedded Applications Thermal Design Guide
Thermal Design Guidelines
4.2 Thermal Specifications
To allow for the optimal operation and long-term reliability of Intel processor-based systems, the
system/processor thermal solution should be designed such that the processor remains within the
minimum and maximum case temperature (T
C
) specifications when operating at or below the TDP
value listed in the
Intel Celeron D Processor Datasheet. Thermal solutions not designed to provide
this level of thermal capability may affect the long-term reliability of the processor and system and
may also increase the risk of activating the Thermal Control Circuit (TCC).
The Celeron D processor introduces a new methodology for managing processor temperatures
through fan speed control. Selection of an appropriate fan speed is based on the temperature
reported by the processor's Thermal Diode. The fan must be turned on to full speed when Tdiode is
at or above Tcontrol, and TC must be maintained at or below TC max as defined by the processor
thermal specification in the processor datasheet. The fan speed may be lowered when the processor
temperature can be maintained below Tcontrol as measured by the thermal diode. Systems
implementing fan speed control must be designed to read temperature values from the diode and
Tcontrol register and take appropriate action. Systems that do not alter the fan speed (always at full
speed) only need to guarantee that the case temperature meets the processor thermal specifications.
The case temperature is defined at the geometric top center of the processor IHS. Analysis
indicates that real applications are unlikely to cause the processor to consume maximum power
dissipation for sustained periods of time. Intel recommends that complete thermal solution designs
target the TDP as indicated in the processor datasheet instead of the maximum processor power
consumption. The Thermal Monitor feature is intended to help protect the processor in the unlikely
event that the application exceeds the TDP recommendation for a sustained period of time. Refer to
the processor datasheet for more information on the Intel Thermal Monitor. In all cases, the
Thermal Monitor feature must be enabled for the processor to remain within specification.
4.3 T
control
T
control
defines the maximum operating temperature for the on-die thermal diode when the thermal
solution fan speed is being controlled by the on-die thermal diode. This parameter allows the
system integrator a method to reduce the acoustic noise of the processor cooling solution while
maintaining compliance with the processor thermal specification.
T
control
and fan speed reduction are not requirements for the Intel Celeron D processor in the
478-pin package but are provided as options for platforms that can use these features. T
control
is
part of the temperature specification that defines temperature for system fan speed management.
The BIOS reads the T
control
value once and configures the fan control chip appropriately. The value
for T
control
will be set during manufacturing and is unique for each processor. The T
control
temperature for a given processor can be obtained by reading IA32_TEMPERATURE_TARGET
MSR in the processor and is in hexadecimal format. For more information on T
control
and fan speed
reduction, refer to the Intel Celeron D Processor Datasheet.