Out Of Specification Detection; Prochot# Signal Pin - Intel P8700 - Core 2 Duo Processor Datasheet

Changes to the temperature can be detected via two programmable thresholds located
in the processor MSRs. These thresholds have the capability of generating interrupts
via the core's local APIC. Refer to the Intel® 64 and IA-32 Architectures Software
Developer's Manuals for specific register and programming details.
5.2

Out of Specification Detection

Overheat detection is performed by monitoring the processor temperature and
temperature gradient. This feature is intended for graceful shutdown before the
THERMTRIP# is activated. If the processor's TM1 or TM2 are triggered and the
temperature remains high, an Out Of Spec status and sticky bit are latched in the
status MSR register and generates a thermal interrupt.
5.3

PROCHOT# Signal Pin

An external signal, PROCHOT# (processor hot), is asserted when the processor die
temperature has reached its maximum operating temperature. If TM1 or TM2 is
enabled, then the TCC will be active when PROCHOT# is asserted. The processor can
be configured to generate an interrupt upon the assertion or deassertion of
PROCHOT#. Refer to the an interrupt upon the assertion or deassertion of PROCHOT#.
Refer to the Intel® 64 and IA-32 Architectures Software Developer's Manuals for
specific register and programming details.
The processor implements a bi-directional PROCHOT# capability to allow system
designs to protect various components from overheating situations. The PROCHOT#
signal is bi-directional in that it can either signal when the processor 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.
Only a single PROCHOT# pin exists at a package level of the processor. When either
core's thermal sensor trips, PROCHOT# signal will be driven by the processor package.
If only TM1 is enabled, PROCHOT# will be asserted regardless of which core is above its
TCC temperature trip point, and both cores will have their core clocks modulated. If
TM2 is enabled then, regardless of which core(s) are above the TCC temperature trip
point, both cores will enter the lowest programmed TM2 performance state. It is
important to note that Intel recommends both TM1 and TM2 to be enabled.
When PROCHOT# is driven by an external agent, if only TM1 is enabled on both cores,
then both processor cores will have their core clocks modulated. If TM2 is enabled on
both cores, then both processor cores will enter the lowest programmed TM2
performance state. It should be noted that Force TM1 on TM2, enabled via BIOS, does
not have any effect on external PROCHOT#. If PROCHOT# is driven by an external
agent when TM1, TM2, and Force TM1 on TM2 are all enabled, then the processor will
still apply only TM2.
PROCHOT# may be used for 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 PROCHOT# (pulled-low)
and activating the TCC, the VR will cool down as a result of reduced processor power
consumption. Bi-directional PROCHOT# 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 TDP. With a properly designed and characterized thermal solution, it is
anticipated that bi-directional PROCHOT# would only be asserted for very short periods
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Thermal Specifications and Design Considerations
Datasheet