Mobile Intel Pentium 4 Processor with 533 MHz Front Side Bus

Mobile Intel
®
Pentium
®
4 Processor with 533 MHz System Bus Datasheet 67
Thermal Specifications and Design Considerations
5.2 Processor Thermal Features
5.2.1 Intel Thermal Monitor
The Intel Thermal Monitor feature helps control the processor temperature by activating the
thermal control circuit (TCC) when the processor silicon reaches its maximum operating
temperature. The TCC reduces processor power consumption by modulating (starting and
stopping) the internal processor core clocks. The Intel Thermal Monitor feature must be
enabled for the processor to be operating within specifications. The temperature at which Intel
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 Intel 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.
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
Figure 15. Guideline Locations for Case Temperature (T
CASE
) Thermocouple Placement
Measure Tcase
A
t this poin
t
Thermal Interface
Material should cover the
entire surface of the
Inte
g
rated Heat S
p
reader
0.689”
17.5 mm
0.689”
17.5 mm
35 mm Package