Intel Pentium 4 Processor in the 478-Pin Package Thermal Design Guidelines

Intel
®
Pentium
®
4 Processor in the 478-Pin Package Thermal Design Guidelines
R
Design Guide 35
Figure 13. Thermal Diode Sensor Time Delay
Processor Temperature
Time in 1/16
th
second intervals
Temperature is averaged
over 1/16
th
second
Temperature is
reported 1/16
th
second later
Processor
temperature
ramp
Processor Temperature
Time in 1/16
th
second intervals
Temperature is averaged
over 1/16
th
second
Temperature is
reported 1/16
th
second later
Processor
temperature
ramp
2.4.6.2 THERMTRIP#
In the event of a catastrophic cooling failure, the processor will automatically shut down when the
silicon temperature has reached approximately ~135 °C. At this point the system bus signal
THERMTRIP# goes active and power needs to 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 processor datasheet for more
information about THERMTRIP#.
2.4.6.3 Thermal Measurement Correlation
There are two independent thermal diodes in the Intel

Pentium

4 processor in the 478-pin
package. One is the on-die thermal diode described in Section 2.4.6.1. 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 isolated devices with no
direct 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. As a result, it is not possible to predict the activation of the thermal
control circuit by monitoring the on-die thermal diode.
2.4.7 Cooling System Failure Warning
If desired, the system may be designed to cool the maximum processor power. In this situation, 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 graceful system shutdown. If no
thermal management action is taken, the silicon temperature may exceed ~135°C causing
THERMTRIP# to go active and shut down the processor. Regardless of the system design
requirements or cooling solution ability, the Thermal Monitor feature must still be enabled to
guarantee proper processor operation.