Intel Pentium M 770 RH80536GE0462M Data Sheet

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#. 

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 

.

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