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asserted until the processor exits the low-power state and the processor junction
temperature drops below the thermal trip point.
If Intel Thermal Monitor automatic mode is disabled, the processor operates out of
specification. Regardless of enabling the automatic or on-demand modes, in the event
of a catastrophic cooling failure, the processor automatically shuts down when the
silicon has reached a temperature of approximately 125°C. At this point the
THERMTRIP# signal goes active. THERMTRIP# activation is independent of processor
activity and does not generate any bus cycles. When THERMTRIP# is asserted, the
processor core voltage must be shut down within the time specified in
5.3
Digital Thermal Sensor
The processor also contains an on die Digital Thermal Sensor (DTS) that can be read
via a MSR (no I/O interface). The DTS is the preferred method of reading the processor
die temperature since it can be located much closer to the hottest portions of the die
and can thus more accurately track the die temperature and potential activation of
processor core clock modulation via the Intel Thermal Monitor. The DTS is only valid
while the processor is in the normal operating state (C0 state).
Unlike traditional thermal devices, the DTS outputs a temperature relative to the
maximum supported operating temperature of the processor (T
responsibility of software to convert the relative temperature to an absolute
temperature. The temperature returned by the digital thermal sensor is always at or
below T
J,max
This bit is also part of the DTS MSR. When this bit is set, the processor is operating out
of specification and immediate shutdown of the system should occur. The processor
operation and code execution is not guaranteed once the activation of the Out of Spec
status bit is set.
The DTS relative temperature readout corresponds to an Intel Thermal Monitor 1
trigger point. When the DTS indicates maximum processor core temperature has been
reached the Intel Thermal Monitor 1 hardware thermal control mechanism activates.
The DTS and Intel Thermal Monitor 1 temperature may not correspond to the thermal
diode reading since the thermal diode is located in a separate portion of the die.
Additionally, the thermal gradient from DTS to thermal diode can vary substantially due
to changes in processor power, mechanical and thermal attach and software
application. The system designer is required to use the DTS to guarantee proper
operation of the processor within its temperature operating specifications.
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 APIC. Refer to the Intel® 64 and IA-32 Intel® Architectures Software
Developer's Manual for specific register and programming details.
5.4
Out of Specification Detection
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 is 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.
66
. Over temperature conditions are detectable via an Out Of Spec status bit.
Thermal Specifications
Chapter
3.
). It is the
J,max
Datasheet
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