Intel Pentium M RH80535GC0211M Data Sheet
Product codes
RH80535GC0211M
Thermal Specifications and Design Considerations
68
Datasheet
When Intel Thermal Monitor 1 is enabled while a high temperature situation exists, the
clocks will be modulated by alternately turning the clocks off and on at a 50% duty
cycle. Cycle times are processor speed dependent and will decrease linearly as
processor core frequencies increase. Once the temperature has returned to a non-
critical level, modulation ceases and TCC goes inactive. A small amount of hysteresis
has been included to prevent rapid active/inactive transitions of the TCC when the
processor temperature is near the trip point. The duty cycle is factory configured and
cannot be modified. Also, automatic mode does not require any additional hardware,
software drivers, or interrupt handling routines. Processor performance will be
decreased by the same amount as the duty cycle when the TCC is active.
The TCC may also be activated via on-demand mode. If bit 4 of the ACPI Intel Thermal
Monitor control register is written to a 1, the TCC will be activated immediately,
independent of the processor temperature. When using on-demand mode to activate
the TCC, the duty cycle of the clock modulation is programmable via bits 3:1 of the
same ACPI Intel Thermal Monitor control register. In automatic mode, the duty cycle is
fixed at 50% on, 50% off, however in on-demand mode, the duty cycle can be
programmed from 12.5% on/ 87.5% off, to 87.5% on/12.5% off in 12.5% increments.
On-demand mode may be used at the same time automatic mode is enabled, however,
if the system tries to enable the TCC via on-demand mode at the same time automatic
mode is enabled and a high temperature condition exists, automatic mode will take
precedence.
An external signal, PROCHOT# (processor hot) is asserted when the processor detects
that its temperature is above the thermal trip point. Bus snooping and interrupt
latching are also active while the TCC is active.
Besides the thermal sensor and thermal control circuit, the Intel Thermal Monitor also
includes one ACPI register, one performance counter register, three Model Specific
Registers (MSR), and one I/O pin (PROCHOT#). All are available to monitor and control
the state of the Intel Thermal Monitor feature. The Intel Thermal Monitor can be
configured to generate an interrupt upon the assertion or deassertion of PROCHOT#.
Note:
PROCHOT# will not be asserted when the processor is in the Stop Grant, Sleep and
Deep Sleep low power states (internal clocks stopped), hence the thermal diode
reading must be used as a safeguard to maintain the processor junction temperature
within maximum specification. If the platform thermal solution is not able to maintain
the processor junction temperature within the maximum specification, the system must
initiate an orderly shutdown to prevent damage. If the processor enters one of the
above low power states with PROCHOT# already asserted, PROCHOT# will remain
asserted until the processor exits the low power state and the processor junction
temperature drops below the thermal trip point.
If Thermal Monitor automatic mode is disabled, the processor will be operating out of
specification. Regardless of enabling the automatic or on-demand modes, in the event
of a catastrophic cooling failure, the processor will automatically shut down when the
silicon has reached a temperature of approximately 125°C. At this point the
THERMTRIP# signal will go 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
.
5.1.4
Digital Thermal Sensor
The Intel Pentium Dual-Core processor also contains an on die digital thermal sensor
that can be read via a MSR (no I/O interface). In a dual core implementation of the
processor, each core will have a unique digital thermal sensor whose temperature is
accessible via processor MSR. The digital thermal sensor 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