Intel Pentium 4 Processor on 90 nm Process Thermal and Mechanical Design Guidelines

Thermal Requirements
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Intel
®
Pentium
®
4 on 90 nm Process Thermal Design Guide 29
3.4.8 Legacy Thermal Management Capabilities
In addition to Thermal Monitor, the Pentium 4 processor on 90 nm process supports the same
thermal management features originally available on the Intel

Pentium

III processor. These
features are the on-die thermal diode and THERMTRIP# signal for indicating catastrophic
thermal failure.
3.4.8.1 On-Die Thermal Diode
There are two independent thermal sensing devices in the Pentium 4 processor on 90 nm process.
One is the on-die thermal diode and the other is in the temperature sensor used for the Thermal
Monitor and for THERMTRIP#. The Thermal Monitor’s temperature sensor and the on-die
thermal diode are independent and physically isolated devices with no defined correlation to one
another. 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.
System integrators should note that there is no defined correlation between the on-die thermal
diode and the processor case temperature. The temperature distribution across the die is affected
by the power being dissipated; type of activity the processor is performing (e.g., integer or
floating point intensive) and the leakage current. The dynamic and independent nature of these
effects makes it difficult to provide a meaningful correlation for the processor population.
System integrators that plan on using the thermal diode for system or component level fan control
to optimize acoustics need to refer to the acoustic fan control, Section 3.6
3.4.8.2 THERMTRIP#
In the event of a catastrophic cooling failure, the processor will automatically shut down when the
silicon temperature has reached its operating limit. At this point the system bus signal
THERMTRIP# goes active and power must be removed from the processor. THERMTRIP# stays
active until RESET# has been initiated. THERMTRIP# activation is independent of processor
activity and does not generate any bus cycles. Refer to the Intel
®
Pentium
®
4 Processor on 90 nm
Process Datasheet for more information about THERMTRIP#.
Like, Thermal Monitor, (PROCHOT# activation temperature), THERMTRIP# is also individually
calibrated during manufacturing. The temperature where THERMTRIP# goes active is roughly
parallel to the thermal profile and greater than the PROCHOT# activation temperature. Once
configured, temperature at which the THERMTRIP# signal is asserted is neither re-configurable
nor accessible to the system.