Thermal
A small amount of hysteresis has been included to prevent rapid active/inactive transitions of the TCC when the processor temperature is near the TCC activation temperature. Once the temperature has dropped below the trip temperature and the hysteresis timer has expired, the operating frequency and voltage transition back to the normal system operating point using the intermediate VID/frequency points. Transition of the VID code will occur first, to insure proper operation as the frequency is increased.
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
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 Transition to Combined TM1 and TM2
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, the processor will immediately transition to the combined TM1/TM2 condition. The processor remains 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, 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 Testability Signals on page 82) 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.
| Intel® Xeon® Processor |
June 2013 | Datasheet – Volume 1 of 2 |
Order No.: | 71 |