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Thermal/Mechanical Specifications and Design Guidelines 41
Thermal Specifications
6.2.2 Adaptive Thermal Monitor
The Adaptive Thermal Monitor feature provides an enhanced method for controlling the
processor temperature when the processor silicon exceeds the Thermal Control Circuit
(TCC) activation temperature. Adaptive Thermal Monitor uses TCC activation to reduce
processor power via a combination of methods. The first method (Frequency/VID
control, similar to Intel
® Thermal Monitor 2 (TM2) in previous generation processors)
involves the processor reducing its operating frequency (using the core ratio multiplier)
and input voltage (using the VID signals). This combination of lower frequency and VID
results in a reduction of the processor power consumption. The second method (clock
modulation, known as Intel
® Thermal Monitor 1 or TM1 in previous generation
processors) reduces power consumption by modulating (starting and stopping) the
internal processor core clocks. The processor intelligently selects the appropriate TCC
method to use on a dynamic basis. BIOS is not required to select a specific method (as
with previous-generation processors supporting TM1 or TM2). The temperature at
which Adaptive Thermal Monitor activates the Thermal Control Circuit is factory
calibrated and is not user configurable. Snooping and interrupt processing are
performed in the normal manner while the TCC is active.
When the TCC activation temperature is reached, the processor will initiate TM2 in
attempt to reduce its temperature. If TM2 is unable to reduce the processor
temperature then TM1 will be also be activated. TM1 and TM2 will work together (clocks
will be modulated at the lowest frequency ratio) to reduce power dissipation and
temperature.
With a properly designed and characterized thermal solution, it is anticipated that the
TCC would only be activated 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. An
under-designed thermal solution that is not able to prevent excessive activation of the
TCC in the anticipated ambient environment may cause a noticeable performance loss,
and in some cases may result in a T
CASE
that exceeds the specified maximum
temperature and may affect the long-term reliability of the processor. In addition, a
thermal solution that is significantly under-designed may not be capable of cooling the
processor even when the TCC is active continuously. Refer to the appropriate Thermal
Mechanical Design Guidelines for information on designing a compliant thermal
solution.
The Intel Thermal Monitor does not require any additional hardware, software drivers,
or interrupt handling routines. The following sections provide more details on the
different TCC mechanisms used by the processor.
6.2.2.1 Frequency/VID Control
When the Digital Temperature Sensor (DTS) reaches a value of 0 (DTS temperatures
reported using PECI may not equal zero when PROCHOT# is activated, see
Section 6.3
for further details), the TCC will be activated and the PROCHOT# signal will be
asserted. This indicates the processors' temperature has met or exceeded the factory
calibrated trip temperature and it will take action to reduce the temperature.
Upon activation of the TCC, the processor will stop the core clocks, reduce the core
ratio multiplier by 1 ratio, and restart the clocks. All processor activity stops during this
frequency transition that occurs within 2 us. Once the clocks have been restarted at the
new lower frequency, processor activity resumes while the voltage requested by the
VID lines is stepped down to the minimum possible for the particular frequency.