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5.1.2
Thermal Metrology
The maximum and minimum case temperatures (T
specifications are meant to help ensure proper operation of the processor.
where Intel recommends T
temperature measurement methodology, refer to the Intel
Process in the 775-Land Package Thermal Design Guidelines.
Figure 5-3. Case Temperature (T
5.2
Processor Thermal Features
5.2.1
Thermal Monitor
The Thermal Monitor feature helps control the processor temperature by activating the TCC when
the processor silicon reaches its maximum operating temperature. The TCC reduces processor
power consumption as needed by modulating (starting and stopping) the internal processor core
clocks. The Thermal Monitor feature must be enabled for the processor to be operating
within specifications. The temperature at which Thermal Monitor activates the thermal control
circuit is not user configurable and is not software visible. Bus traffic is snooped in the normal
manner, and interrupt requests are latched (and serviced during the time that the clocks are on)
while the TCC is active.
When the Thermal Monitor feature is enabled, and a high temperature situation exists (i.e., TCC is
active), the clocks will be modulated by alternately turning the clocks off and on at a duty cycle
specific to the processor (typically 30–50%). Clocks often will not be off for more than
3.0 microseconds when the TCC is active. Cycle times are processor speed dependent and will
decrease as processor core frequencies increase. A small amount of hysteresis has been included to
prevent rapid active/inactive transitions of the TCC when the processor temperature is near its
maximum operating temperature. Once the temperature has dropped below the maximum
operating temperature, and the hysteresis timer has expired, the TCC goes inactive and clock
modulation ceases.
Datasheet
Thermal Specifications and Design Considerations
C
thermal measurements should be made. For detailed guidelines on
C
) Measurement Location
C
37.5 mm
37.5 mm
) are specified in
Table
5-1. These temperature
Figure 5-3
®
®
Pentium
4 Processor on 90 nm
Measure T
Measure T
at this point
at this point
C
C
(geometric center of the package)
(geometric center of the package)
illustrates
79
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