sbsrinivas :
... Intel Xeon E5 1650 v4 ... Tcase 69 degree Celsius ... the temperature indicated by lm-sensors is not the same as Tcase ... how do I find out the temperature at the IHS (Integrated Heat Spreader) in Linux, or derive the critical core temperature for this processor?
Your Xeon E5 1650 v4 is a Broadwell 22nm 6 Core / 12 Thread 140 Watt TDP processor. It has a soldered IHS and is essentially a workstation / server branded i7 6850K -
http://ark.intel.com/products/94188/Intel-Core-i7-6850K-Processor-15M-Cache-up-to-3_80-GHz
Tcase is a
factory only temperature measured on the external surface of the IHS. For
lab testing only,
engineering samples are used. A groove is cut into the surface of the IHS where a "thermocouple" is embedded at the center, which does
not exist on retail or wholesale processors.
As you've already stated, Tcase is
not Core temperature. Core temperatures are measured at the heat sources near the transistor "Junctions" inside each of the Cores, where temperatures are considerably higher than Tcase.
Tcase is
measured on the IHS, but it's also
calculated based on stock cooler TDP and processor TDP, which is primarily why specifications vary. Tcase is a useful specification for cooling solution developers and data centers, but it's misleading, confusing and unnecessary for users. Throttle temperature (Tj Max) is the limiting Thermal Specification;
not Tcase.
The Tj Max specification for your E5 1650 v4 is 100°C. Although most processors Throttle at 100°C (212°F), it’s not advisable to run your CPU near the thermal limit, just as you wouldn't run a vehicle with the temperature gauge pegged in the red "hot" zone. If your hottest Core is near it's specified Tj Max Throttle temperature, then your CPU is already too hot.
The consensus among highly experienced and well informed system builders is that cooler is better for ultimate stability, performance and longevity. Experts agree it's prudent to observe a reasonable thermal margin below Tj Max. So regardless of environmental conditions, hardware configurations, workloads or any other variables,
Core temperatures above 85°C aren't recommended.
Here's the operating range for Core temperature:
Core temperatures increase and decrease with Ambient temperature. Idle temperatures below 25°C are generally due to Ambient temperatures below 22°C.
CT
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