User Guide

Thermal Management
88 Datasheet, Volume 1 of 2
5.1.5.4 Bi-Directional PROCHOT#
By default, the PROCHOT# signal is set to input only. When configured as an input or
bi-directional signal, PROCHOT# can be used for thermally protecting other platform
components should they overheat as well. When PROCHOT# is driven by an external
device:
• The package will immediately transition to the lowest P-State (Pn) supported by the
processor IA cores and graphics cores. This is contrary to the internally-generated
Adaptive Thermal Monitor response.
• Clock modulation is not activated.
The processor package will remain at the lowest supported P-state until the system de-
asserts PROCHOT#. The processor can be configured to generate an interrupt upon
assertion and de-assertion of the PROCHOT# signal.
When PROCHOT# is configured as a bi-directional signal and PROCHOT# is asserted by
the processor, it is impossible for the processor to detect a system assertion of
PROCHOT#. The system assertion will have to wait until the processor de-asserts
PROCHOT# before PROCHOT# action can occur due to the system assertion. While the
processor is hot and asserting PROCHOT#, the power is reduced but the reduction rate
is slower than the system PROCHOT# response of < 100 us. The processor thermal
control is staged in smaller increments over many milliseconds. This may cause several
milliseconds of delay to a system assertion of PROCHOT# while the output function is
asserted.
5.1.5.5 Voltage Regulator Protection using PROCHOT#
PROCHOT# may be used for thermal protection of voltage regulators (VR). System
designers can create a circuit to monitor the VR temperature and assert PROCHOT#
and, if enabled, activate the TCC when the temperature limit of the VR is reached.
When PROCHOT# is configured as a bi-directional or input only signal, if the system
assertion of PROCHOT# is recognized by the processor, it will result in an immediate
transition to the lowest P-State (Pn) supported by the processor IA cores and graphics
cores. 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. Overall, the system
thermal design should allow the power delivery circuitry to operate within its
temperature specification even while the processor is operating at its TDP.
5.1.5.6 Thermal Solution Design and PROCHOT# Behavior
With a properly designed and characterized thermal solution, it is anticipated that
PROCHOT# will only be asserted for very short periods of time when running the most
power intensive applications. The processor performance impact due to these brief
periods of TCC activation is expected to be so minor that it would be immeasurable.
However, 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.
• Result in prolonged operation at or above the specified maximum junction
temperature and affect the long-term reliability of the processor.
• May be incapable of cooling the processor even when the TCC is active continuously
(in extreme situations).