Intel 2 Duo T7800 LE80537GG0644M User Manual

Datasheet

87

Overheat detection is performed by monitoring the processor temperature and 

temperature gradient. This feature is intended for graceful shut down before the 

THERMTRIP# is activated. If the processor’s Intel Thermal Monitor 1 or 2 are triggered 

and the temperature remains high, an “Out Of Spec” status and sticky bit are latched in 

the status MSR register and generates thermal interrupt. 

An external signal, PROCHOT# (processor hot), is asserted when the processor die 

temperature has reached its maximum operating temperature. If Intel Thermal Monitor 

1 or 2 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 Intel® 64 and IA-32 Architectures Software Developer’s 

Manual 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, the PROCHOT# signal will be driven by the processor 

package. If only Intel Thermal Monitor 1 is enabled, PROCHOT# will be asserted and 

only the core that is above TCC temperature trip point will have its core clocks 

modulated. If Intel Thermal Monitor 2 is enabled, then regardless of which core(s) are 

above TCC temperature trip point, both cores will enter the lowest programmed Intel 

Thermal Monitor 2 performance state. It is important to note that Intel recommends 

both Intel Thermal Monitor 1 and 2 to be enabled.

When PROCHOT# is driven by an external agent, if only Intel Thermal Monitor 1 is 

enabled on both cores, then both processor cores will have their core clocks modulated. 

If Intel Thermal Monitor 2 is enabled on both cores, then both processor cores will 

enter the lowest programmed Intel Thermal Monitor 2 performance state. It should be 

noted that Force Intel Thermal Monitor 1 on Intel Thermal Monitor 2, enabled via BIOS, 

does not have any effect on external PROCHOT#. If PROCHOT# is driven by an external 

agent when Intel Thermal Monitor 1, Intel Thermal Monitor 2, and Force Intel Thermal 

Monitor 1 on Intel Thermal Monitor 2 are all enabled, then the processor will still apply 

only Intel Thermal Monitor 2.

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 

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.

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