Intel X5472 Data Sheet - Page 93

Thermal Specifications 6.2.3 6.2.4 Series must not rely on software usage of this mechanism to limit the processor temperature. If bit 4 of the IA32_CLOCK_MODULATION MSR is set to a '1', the processor will immediately reduce its power consumption via modulation (starting and stopping) of the internal core clock, independent of the processor temperature. When using On-Demand mode, the duty cycle of the clock modulation is programmable via bits 3:1 of the same IA32_CLOCK_MODULATION MSR. 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 in conjunction with the Thermal Monitor; however, if the system tries to enable On-Demand mode at the same time the TCC is engaged, the factory configured duty cycle of the TCC will override the duty cycle selected by the On-Demand mode. PROCHOT# Signal An external signal, PROCHOT# (processor hot) is asserted when the processor die temperature of any processor cores reaches its factory configured trip point. If Thermal Monitor is enabled (note that Thermal Monitor 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#. Refer to the Intel® 64 and IA-32 Architectures Software Developer's Manual for specific register and programming details. PROCHOT# is designed to assert at or a few degrees higher than maximum TCASE when dissipating TDP power, and cannot be interpreted as an indication of processor case temperature. This temperature delta accounts for processor package, lifetime and manufacturing variations and attempts to ensure the Thermal Control Circuit is not activated below maximum TCASE when dissipating TDP power. There is no defined or fixed correlation between the PROCHOT# trip temperature, or the case temperature. Thermal solutions must be designed to the processor specifications and cannot be adjusted based on experimental measurements of TCASE, or PROCHOT#. FORCEPR# Signal The FORCEPR# (force power reduction) input can be used by the platform to cause the Quad-Core Intel® Xeon® Processor 5400 Series to activate the TCC. If the Thermal Monitor is enabled, the TCC will be activated upon the assertion of the FORCEPR# signal. Assertion of the FORCEPR# signal will activate TCC for all processor cores. The TCC will remain active until the system deasserts FORCEPR#. FORCEPR# is an asynchronous input. FORCEPR# can be used to thermally protect other system components. To use the VR as an example, when FORCEPR# is asserted, the TCC circuit in the processor will activate, reducing the current consumption of the processor and the corresponding temperature of the VR. It should be noted that assertion of FORCEPR# does not automatically assert PROCHOT#. As mentioned previously, the PROCHOT# signal is asserted when a high temperature situation is detected. A minimum pulse width of 500 µs is recommended when FORCEPR# is asserted by the system. Sustained activation of the FORCEPR# signal may cause noticeable platform performance degradation. Refer to the appropriate platform design guidelines for details on implementing the FORCEPR# signal feature. 93