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Thermal Management Logic and Thermal Monitor
4.2.5
System Considerations
Intel requires the Thermal Monitor and Thermal Control Circuit to be enabled for all Celeron D
processors in the 775-land LGA package based systems. The thermal control circuit is intended to
protect against short term thermal excursions that exceed the capability of a well designed
processor thermal solution. Thermal Monitor should not be relied upon to compensate for a thermal
solution that does not meet the thermal profile up to the thermal design power (TDP).
Each application program has its own unique power profile, although the profile has some
variability due to loop decisions, I/O activity and interrupts. In general, compute intensive
applications with a high cache hit rate dissipate more processor power than applications that are
I/O intensive or have low cache hit rates.
The processor thermal design power (TDP) is based on measurements of processor power
consumption while running various high power applications. This data is used to determine those
applications that are interesting from a power perspective. These applications are then evaluated in
a controlled thermal environment to determine their sensitivity to activation of the thermal control
circuit. This data is used to derive the TDP targets published in the processor datasheet.
A system designed to meet the thermal profile at TDP and T
processor datasheet or datasheet greatly reduces the probability of real applications causing the
thermal control circuit to activate under normal operating conditions. Systems that do not meet
these specifications could be subject to more frequent activation of the thermal control circuit
depending upon ambient air temperature and application power profile. Moreover, if a system is
significantly under designed, there is a risk that the Thermal Monitor feature will not be capable of
maintaining a safe operating temperature and the processor could shutdown and signal
THERMTRIP#.
For information regarding THERMTRIP#, refer to the processor datasheet and to
"Cooling System Failure Warning" on page
4.2.6
Operating System and Application Software Considerations
The Thermal Monitor feature and its thermal control circuit work seamlessly with ACPI compliant
operating systems. The Thermal Monitor feature is transparent to application software since the
processor bus snooping, ACPI timer, and interrupts are active at all times.
4.2.7
On-Die Thermal Diode
There are two independent thermal sensing devices in the Celeron D Processor in the 775-land
LGA package. One is the on-die thermal diode and the other is in the temperature sensor used for
the Thermal Monitor (and Thermal Monitor 2) and for THERMTRIP#. The Thermal Monitor's
temperature sensor and the on-die thermal diode are independent and physically isolated devices.
Circuit constraints and performance requirements prevent the Thermal Monitor's temperature
sensor and the on-die thermal diode from being located at the same place on the silicon. The
temperature distribution across the die may result in significant temperature differences between
the on-die thermal diode and the Thermal Monitor's temperature sensor. This temperature
variability across the die is highly dependent on the application being run. As a result, it is not
possible to predict the activation of the thermal control circuit by monitoring the on-die thermal
diode.
Intel
26
®
®
Celeron
D Processor in the 775-Land LGA Package Thermal Design Guide
values published in the
C-MAX
28.
Section 4.2.8.1,
Order #303730
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