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A system designed to meet the thermal profile specification published in the processor
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 reducing the processor power and temperature
and the processor could shutdown and signal THERMTRIP#.
For information regarding THERMTRIP#, refer to the processor datasheet and to
Section 4.2.8 of this Thermal Design Guidelines.
4.2.7
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.
4.2.8
THERMTRIP# Signal
In the event of a catastrophic cooling failure, the processor will automatically shut
down when the silicon temperature has exceeded the TCC activation temperature by
approximately 20 to 25 °C. At this point the system bus signal THERMTRIP# goes
active and power must be removed from the processor. THERMTRIP# activation is
independent of processor activity and does not generate any bus cycles. Refer to the
processor datasheet for more information about THERMTRIP#.
The temperature where the THERMTRIP# signal goes active is individually calibrated
during manufacturing and once configuration cannot be changed.
4.2.9
Cooling System Failure Warning
It may be useful to use the PROCHOT# signal as an indication of cooling system
failure. Messages could be sent to the system administrator to warn of the cooling
failure, while the thermal control circuit would allow the system to continue
functioning or allow a normal system shutdown. If no thermal management action is
taken, the silicon temperature may exceed the operating limits, causing THERMTRIP#
to activate and shut down the processor. Regardless of the system design
requirements or thermal solution ability, the Thermal Monitor feature must still be
enabled to ensure proper processor operation.
36
Thermal Management Logic and Thermal Monitor Feature
Thermal and Mechanical Design Guidelines
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