Intel X5472 Mechanical Design Guidelines - Page 20

Thermal/Mechanical Reference Design 2.2.2 20 processor operating frequency (via the bus multiplier) and input voltage (via the VID signals). Please refer to the Quad-Core Intel® Xeon® Processor 5400 Series Datasheet for further details on TM and TM2. PROCHOT# is designed to assert at or a few degrees higher than maximum TCASE (as specified by the thermal profile) when dissipating TDP power, and can not 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# assertion temperature and the case temperature. However, with the introduction of the Digital Thermal Sensor (DTS) on the Quad-Core Intel® Xeon® Processor 5400 Series, the DTS reports a relative offset below the PROCHOT# assertion (see Section 2.2.2 for more details on the Digital Thermal Sensor). Thermal solutions must be designed to the processor specifications (i.e Thermal Profile) and can not be adjusted based on experimental measurements of TCASE, PROCHOT#, or Digital Thermal Sensor on random processor samples. By taking advantage of the Thermal Monitor features, system designers may reduce thermal solution cost by designing to the Thermal Design Power (TDP) instead of maximum power. TDP should be used for processor thermal solution design targets. TDP is not the maximum power that the processor can dissipate. TDP is based on measurements of processor power consumption while running various high power applications. This data set is used to determine those applications that are interesting from a power perspective. These applications are then evaluated in a controlled thermal environment to determine their sensitivity to activation of the thermal control circuit. This data set is then used to derive the TDP targets published in the processors datasheet. The Thermal Monitor can protect the processors in rare workload excursions above TDP. Therefore, thermal solutions should be designed to dissipate this target power level. The thermal management logic and thermal monitor features are discussed in extensive detail in the Quad-Core Intel® Xeon® Processor 5400 Series Datasheet. In addition, on-die thermal management features called THERMTRIP# and FORCEPR# are available on the Quad-Core Intel® Xeon® Processor 5400 Series. They provide a thermal management approach to support the continued increases in processor frequency and performance. Please see the Quad-Core Intel® Xeon® Processor 5400 Series Datasheet for guidance on these thermal management features. Digital Thermal Sensor The Quad-Core Intel® Xeon® Processor 5400 Series include on-die temperature sensor feature called Digital Thermal Sensor (DTS). The DTS uses the same sensor utilized for TCC activation. Each individual processor is calibrated so that TCC activation occurs at a DTS value of 0. The temperature reported by the DTS is the relative offset in PECI counts below the onset of the TCC activation and hence is negative. Changes in PECI counts are roughly linear in relation to temperature changes in degrees Celsius. For example, a change in PECI count by '1' represents a change in temperature of approximately 1°C. However, this linearity cannot be guaranteed as the offset below TCC activation exceeds 20-30 PECI counts. Also note that the DTS will not report any values above the TCC activation temperature, it will simply return 0 in this case. The DTS facilitates the use of multiple thermal sensors within the processor without the burden of increasing the number of thermal sensor signal pins on the processor package. Operation of multiple DTS will be discussed in more detail in Section 2.2.4. Also, the DTS utilizes thermal sensors that are optimally located when compared with thermal diodes available with legacy processors. This is achieved as a result of a Quad-Core Intel® Xeon® Processor 5400 Series TMDG