Question How is Tj. Max Calculated?

[Cpt Snake]

I have a 6 core processor. (Intel Core i5-10600 (base stroke: 3.30GHz; socket: LGA1200; 65 watt) Each one has its own temperature according to "Core Temp"., So how is the Tj Max calculated. Is it an average or based on one cores temp? Thanks.

 

[drea.drechsler]

With respect to us users Tjmax is not calculated, it's a specification provided by device manufacturers. The designers determine it as a part of the FIT determinations and is calculated stochastically using life test data from large sample tests. Key point is it's not an absolute.

You can get into the meat of it here:
https://www.renesas.com/us/en/document/qsg/calculation-semiconductor-failure-rates

So, they could simply slide the T(stress) temperature values up and down in the calculations and determine how it affects product life in expected use-age. They can then bounce that against warranty liability calculations (if it's set too high), factory yield (if set so low that you throw away good die) to determine the most economical point to set it at.

The way I can imagine it working is engineers will provide a range of possible values and a recommendation. It's up to management to balance warranty liability, market good will and factory yield to arrive at the final number. The way it actually works depends on a company's culture.

 

[TerryLaze]

For intel Tj max is 100 degrees C and it's not calculated but there is a probe inside the CPU that tells the CPU but also any software that asks what the current temp is.
As drechsler said it's basically a little below the failure point which is 110 for intel, at 100 the CPU throttles down hard to keep from reaching higher.

Tj max is the temp of the whole die measured at a specific point and not the individual cores, the core temp is just that the temp of the cores.

 

[Cpt Snake]

OK, I got it Thanks to both of you. 😀