Datasheet 81
Thermal Specifications and Design Considerations
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. Contact your Intel representative for further
details and documentation.
5.2.4 FORCEPR# Signal Pin
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 de-
asserts 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.
It should be noted 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. Contact your Intel representative for further details and
documentation.