This was a thread on calculating TJunction on Intel Processors to include C2Ds over on the Intel forums from a while back. This was an Intel rep response to dev questions.
My understanding of this is that there is no specific Tjunction value for the C2Ds and it is not readable by software... so what is TAT reading?
Will need CompuTronix to translate for us I think.
The processors with a processor signature (CPUID) of 00000F30h through 00000F64h implement the IA32_TEMPERATURE_TARGET (msr 1A2h). For those processors, IA32_TEMPERATURE_TARGET[15:8] is an offset value that must be added to a BASE value which is package dependent and is specified in the appropriate data sheet for the processor. For most but not all, the BASE value is 50C.
For those processors, it is assumed that temperature measurements are obtained from the thermal diode which is connected to base board management controller that also contains a fan speed controller. If the temperature read via the diode is above the BASE + IA32_TEMPERATURE_TARGET[15:8] (offset) then the processor fan is expected to be operating at it’s maximum RPM. Any temperature below that is below base + offset may scale the fan speed down.
Note Tj is not a fixed value and the IA32_TEMPERATURE_TARGET[15:8] value can vary from part to part. Tj is also not software readable.
For the processors with a processor signature of 000006Fxh and 0001066xh the IA32_TEMPERATURE_TARGET[15:8] specifies an offset (below) the PROCHOT# assertion point. For these processors the relative temperature is read via the PECI interface by the base board management controller that also contains the fan speed controller. In the case of the PECI interface the fan speed controller knows that it must spin the fans at their max RPM if the value read from the PECI interface is less than the value from IA32_TEMPERATURE_TARGET[15:8]. Any value greater than IA32_TEMPERATURE_TARGET[15:8] read on the PECI interface indicates the processor is not operating in a hot condition and the fans can be scalled back to a lower RPM.
To support transition mainstream desktop platforms where PECI may not be supported or implemented the Conroe processor (Intel® Core™2 processor) added the BASE + OFFSET method used by the Pentium® 4 processor and temperature reading via the thermal diode. However the OFFSET value is loacated in the THERM_DIODE_OFFSET register (msr 3Fh). THERM_DIODE_OFFSET contains a valid bit and an offset value. If THERM_DIODE_OFFSET[7] is set to 1, then THERM_DIODE_OFFSET[4:0] contains a valid offset value which can be used to program the fan speed controller using the BASE + OFFSET. If THERM_DIODE_OFFSET[7] is cleared to 0 then the thermal diode method of reading the processor temperature and controlling the fans is not available.
Some steppings of the mobile Intel® Core™2 processor do indicate Tj to be approximately 85 or 100 via a single bit in the EXT_CONFIG register (msr 0EEh) but desktop, workstation and server processors do not. Nor is there a register implemented in those processors that software can read to get the Tj value for either the Pentium® 4 processor, Intel® Xeon® processors or Intel® Core™2 processors.
In all implementations the IA21_THERM_STATUS[22:16] value is relative to PROCHOT assertion and not an absolute temperature.
My understanding of this is that there is no specific Tjunction value for the C2Ds and it is not readable by software... so what is TAT reading?
Will need CompuTronix to translate for us I think.
The processors with a processor signature (CPUID) of 00000F30h through 00000F64h implement the IA32_TEMPERATURE_TARGET (msr 1A2h). For those processors, IA32_TEMPERATURE_TARGET[15:8] is an offset value that must be added to a BASE value which is package dependent and is specified in the appropriate data sheet for the processor. For most but not all, the BASE value is 50C.
For those processors, it is assumed that temperature measurements are obtained from the thermal diode which is connected to base board management controller that also contains a fan speed controller. If the temperature read via the diode is above the BASE + IA32_TEMPERATURE_TARGET[15:8] (offset) then the processor fan is expected to be operating at it’s maximum RPM. Any temperature below that is below base + offset may scale the fan speed down.
Note Tj is not a fixed value and the IA32_TEMPERATURE_TARGET[15:8] value can vary from part to part. Tj is also not software readable.
For the processors with a processor signature of 000006Fxh and 0001066xh the IA32_TEMPERATURE_TARGET[15:8] specifies an offset (below) the PROCHOT# assertion point. For these processors the relative temperature is read via the PECI interface by the base board management controller that also contains the fan speed controller. In the case of the PECI interface the fan speed controller knows that it must spin the fans at their max RPM if the value read from the PECI interface is less than the value from IA32_TEMPERATURE_TARGET[15:8]. Any value greater than IA32_TEMPERATURE_TARGET[15:8] read on the PECI interface indicates the processor is not operating in a hot condition and the fans can be scalled back to a lower RPM.
To support transition mainstream desktop platforms where PECI may not be supported or implemented the Conroe processor (Intel® Core™2 processor) added the BASE + OFFSET method used by the Pentium® 4 processor and temperature reading via the thermal diode. However the OFFSET value is loacated in the THERM_DIODE_OFFSET register (msr 3Fh). THERM_DIODE_OFFSET contains a valid bit and an offset value. If THERM_DIODE_OFFSET[7] is set to 1, then THERM_DIODE_OFFSET[4:0] contains a valid offset value which can be used to program the fan speed controller using the BASE + OFFSET. If THERM_DIODE_OFFSET[7] is cleared to 0 then the thermal diode method of reading the processor temperature and controlling the fans is not available.
Some steppings of the mobile Intel® Core™2 processor do indicate Tj to be approximately 85 or 100 via a single bit in the EXT_CONFIG register (msr 0EEh) but desktop, workstation and server processors do not. Nor is there a register implemented in those processors that software can read to get the Tj value for either the Pentium® 4 processor, Intel® Xeon® processors or Intel® Core™2 processors.
In all implementations the IA21_THERM_STATUS[22:16] value is relative to PROCHOT assertion and not an absolute temperature.
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