Intel Pga478 Data Sheet - Page 66

Intel® Celeron® Processor 1.66 GHz/1.83 GHz-Thermal Specifications and Design Considerations 5.1.4 5.1.5 5.1.6 Digital Thermal Sensor The Intel® Celeron® Processor 1.66 GHz/1.83 GHz also contains an on die digital thermometer that can be read via a MSR (no I/O interface). The digital thermometer shares the thermal sensor of the Intel Thermal Monitor. Intel® Celeron® Processor 1.66 GHz/1.83 GHz has a unique digital thermometer whose temperature is accessible via processor MSR. The digital 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 potential activation of processor throttling via the Thermal Monitor. Unlike traditional thermal devices, the Digital Thermometer outputs a temperature relative to the maximum supported operating temperature of the processor (TJ,max). It is the responsibility of software to convert the relative temperature to an absolute temperature. The temperature returned by the Digital Thermometer is always at or below TJ,max. Over temperature conditions are detectable via an Out Of Spec status bit. This bit is also part of the Digital Thermometer MSR. When this bit is set, the processor is operating out of specification and immediate shutdown of the system should occur. The processor operation and code execution is not guaranteed once the activation of the Out of Spec status bit is set. The Digital Thermal Sensor (DTS) relative temperature readout corresponds to the thermal monitor (TM1/TM2) trigger points. When the DTS indicates maximum processor core temperature has been reached the TM1 or TM2 hardware thermal control mechanism activates. The DTS and TM1/TM2 temperature may not correspond to the thermal diode reading since the thermal diode is located in a separate portion of the die and thermal gradient between the individual core DTS. Additionally, the thermal gradient from DTS to thermal diode can vary substantially due to changes in processor power, mechanical and thermal attach and software application. The system designer is required to use the DTS to guarantee proper operation of the processor within its temperature operating specifications. Out of Specification Detection Overheat detection is performed by monitoring the processor temperature and temperature gradient. This feature is intended for graceful shut down before the THERMTRIP# is activated. If the processor's TM1 or TM2 are triggered and the temperature remains high, an "Out Of Spec" status and sticky bit are latched in the status MSR register and generates thermal interrupt. PROCHOT# Signal Pin An external signal, PROCHOT# (processor hot), is asserted when the processor die temperature has reached its maximum operating temperature. If the Intel Thermal Monitor 1 (TM1) or Intel Thermal Monitor 2 (TM2) is enabled (note that the TM1 or TM2 must be enabled for the processor to be operating within specification), the TCC is active when PROCHOT# is asserted. The processor can be configured to generate an interrupt upon the assertion or deassertion of PROCHOT#. If the processor die cools down below maximum operating temperature (Tjmax) either due to TCC activation or an external event, PROCHOT# automatically de-asserts and the processor resumes normal operation. Refer to the Intel® 64 and IA-32 Architectures Software Developer's Manuals for specific register and programming details. Intel® Celeron® Processor 1.66 GHz/1.83 GHz DS 66 January 2007 Order Number: 315876-002