Originally posted by: abhatia
This Intel link seems to describe TJmax for the Core 2 Duo Wolfdales as 72.4C. That doesn't seem correct. Can someone explain the difference between Intel's definition of TJmax and the definition of TJmax as used in CoreTemp and RealTemp?
Thermal Specification: The thermal specification shown is the maximum case temperature at the maximum Thermal Design Power (TDP) value for that processor. It is measured at the geometric center on the topside of the processor integrated heat spreader. For processors without integrated heat spreaders such as mobile processors, the thermal specification is referred to as the junction temperature (Tj). The maximum junction temperature is defined by an activation of the processor Intel® Thermal Monitor. The Intel Thermal Monitor?s automatic mode is used to indicate that the maximum TJ has been reached.
http://processorfinder.intel.c...ails.aspx?sSpec=SLAPL#
The thermal design limit of 72.4, refers to maximum temp of Tcase (ie, temperature of casing of cpu as measured at geometric center of IHS).
Tjmax is max temp of the core....read bryanW1995 description above.
According to intel white papers, when the core temp reaches Tjmax/TCC, for example 95C, that should roughly correspond to 72.4C measured at Tcase ASSUMING 1) you milled a channel in the geometric center of IHS and placed an accurate thermocouple, 2) TDP is 65W, 3) using intel's cooler, 4)loading the cpu with the exact program intel uses for testing and 5) it is an "average" chip. But that relationship is not guaranteed, as it will vary cpu to cpu....See intels exact less than straightforward verbage....
"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."
Note, you will not see this gradient by comparing cpu to core temps. To go from core temps (on die diodes) to cpu temps (diode between the cores) you only pass through die subtrate, which has a thermal conductance of over 100 w/m*k. To get to true Tcase temps you pass through TIM1 which has a thermal conductance ~20x less than die, and IHS hence the much larger gradient through the higher resistance material...when high TDP is achieved.
http://www.flomerics.com/floth...hnical_papers/t324.pdf
(typical thermal conductivities)
Unless you place a thermocouple in IHS, the largest gradient you will see from core temp to cpu temp (diode between the cores), is at most roughly 5C.
see gradients....figure 5
http://arxiv.org/ftp/arxiv/papers/0709/0709.1861.pdf
Intel still will tell you to use cpu temps, as they should be higher than tcase, but that gives an extra layer of security especially since cpu temps can be calibrated poorly and thus inaccurate. Not to mention ..."For every 10°C rise above the operating range means a halving of the mean time between failures."
http://www.intel.com/support/p...ntium/sb/CS-011039.htm
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