Intel Pentium D 940 HH80553PG0884M User Manual

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As a bi-directional signal, PROCHOT# allows for some protection of various components 

from over-temperature situations. The PROCHOT# signal is bi-directional in that it can 

either signal when the processor (either core) has reached its maximum operating 

temperature or be driven from an external source to activate the TCC. The ability to 

activate the TCC via PROCHOT# can provide a means for thermal protection of system 

components.

Bi-directional PROCHOT# (if enabled) can allow VR thermal designs to target maximum 

sustained current instead of maximum current. Systems should still provide proper 

cooling for the VR, and rely on bi-directional PROCHOT# only as a backup in case of 

system cooling failure. The system thermal design should allow the power delivery 

circuitry to operate within its temperature specification even while the processor is 

operating at its Thermal Design Power. With a properly designed and characterized 

thermal solution, it is anticipated that bi-directional PROCHOT# would only be asserted 

for very short periods of time when running the most power intensive applications. An 

under-designed thermal solution that is not able to prevent excessive assertion of 

PROCHOT# in the anticipated ambient environment may cause a noticeable 

performance loss. Refer to the Voltage Regulator-Down (VRD) 10.1 Design Guide for 

Desktop Socket 775 for details on implementing the bi-directional PROCHOT# feature.

The FORCEPR# (force power reduction) input can be used by the platform to cause the 

processor (both cores) to activate the TCC. If the Thermal Monitor is enabled, the TCC 

will be activated upon the assertion of the FORCEPR# signal. The TCC will remain active 

until the system deasserts FORCEPR#. FORCEPR# is an asynchronous input.

FORCEPR# can be used to thermally protect other system components. To use the VR 

as an example, when the FORCEPR# pin is asserted, the TCC circuit in the processor 

(both cores) will activate, reducing the current consumption of the processor and the 

corresponding temperature of the VR. 

Note that assertion of the FORCEPR# does not automatically assert PROCHOT#. As 

mentioned previously, the PROCHOT# signal is asserted when a high temperature 

situation is detected. A minimum pulse width of 500 µs is recommend when the 

FORCEPR# is asserted by the system. Sustained activation of the FORCEPR# pin may 

cause noticeable platform performance degradation.

One application is the thermal protection of voltage regulators (VR). System designers 

can create a circuit to monitor the VR temperature and activate the TCC when the 

temperature limit of the VR is reached. By asserting FORCEPR# (pulled-low) and 

activating the TCC, the VR can cool down as a result of reduced processor power 

consumption. FORCEPR# can allow VR thermal designs to target maximum sustained 

current instead of maximum current. Systems should still provide proper cooling for the 

VR, and rely on FORCEPR# only as a backup in case of system cooling failure. The 

system thermal design should allow the power delivery circuitry to operate within its 

temperature specification even while the processor is operating at its Thermal Design 

Power. With a properly designed and characterized thermal solution, it is anticipated 

that FORCEPR# would only be asserted for very short periods of time when running the 

most power intensive applications. An under-designed thermal solution that is not able 

to prevent excessive assertion of FORCEPR# in the anticipated ambient environment 

may cause a noticeable performance loss. Refer to the Voltage Regulator-Down (VRD) 

10.1 Design Guide for Desktop Socket 775 for details on implementing the FORCEPR# 

feature.