Intel BX80601920 Data Sheet - Page 78

Thermal Specifications 6.2.2.2 6.2.2.3 6.2.2.4 6.2.2.5 Clock Modulation Clock modulation is a second method of thermal control available to the processor. Clock modulation is performed by rapidly turning the clocks off and on at a duty cycle that should reduce power dissipation by about 50% (typically a 30-50% duty cycle). Clocks often will not be off for more than 32 µs when the TCC is active. Cycle times are independent of processor frequency. The duty cycle for the TCC, when activated by the Thermal Monitor, is factory configured and cannot be modified. It is possible for software to initiate clock modulation with configurable duty cycles. 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. Immediate Transiton to combined TM1 and TM2 As mentioned above, when the TCC is activated, the processor will sequentially step down the ratio multipliers and VIDs in an attempt to reduce the silicon temperature. If the temperature continues to increase and exceeds the TCC activation temperature by approximately 5 °C before the lowest ratio/VID combination has been reached, then the processor will immediately transition to the combined TM1/TM2 condition. The processor will remain in this state until the temperature has dropped below the TCC activation point. Once below the TCC activation temperature, TM1 will be discontinued and TM2 will be exited by stepping up to the appropriate ratio/VID state. Critical Temperature Flag If TM2 is unable to reduce the processor temperature, then TM1 will be also be activated. TM1 and TM2 will then work together to reduce power dissipation and temperature. It is expected that only a catastrophic thermal solution failure would create a situation where both TM1 and TM2 are active. If TM1 and TM2 have both been active for greater than 20 ms and the processor temperature has not dropped below the TCC activation point, then the Critical Temperature Flag in the IA32_THERM_STATUS MSR will be set. This flag is an indicator of a catastrophic thermal solution failure and that the processor cannot reduce its temperature. Unless immediate action is taken to resolve the failure, the processor will probably reach the Thermtrip temperature (see Section 6.2.3 Thermtrip Signal) within a short time. To prevent possible permanent silicon damage, Intel recommends removing power from the processor within ½ second of the Critical Temperature Flag being set. PROCHOT# Signal An external signal, PROCHOT# (processor hot), is asserted when the processor core temperature has exceeded its specification. If Adaptive Thermal Monitor is enabled (note it must be enabled for the processor to be operating within specification), the TCC will be active when PROCHOT# is asserted. The processor can be configured to generate an interrupt upon the assertion or deassertion of PROCHOT#. Although the PROCHOT# signal is an output by default, it may be configured as bidirectional. When configured in bi-directional mode, it is either an output indicating the processor has exceeded its TCC activation temperature or it can be driven from an 78 Datasheet