I have been running an i7 4790k in my system for years now. Later last year it started to get incredibly hot as soon as the work load increased. I would get low 30s to high 20s in idle but could not put it under high/full load without reaching scary high 80 to 90C temps. With Prime95 it would even reach TJmax and start to throttle.
I contacted the support (still under warranty) and they told me the cpu needed to be replaced. They sent me a used unit from the warehouse that was in "good" condition. In the tests I did right away it was running no hotter than 50C under full load.
Now, 5 months later, the replacement cpu has developed the same problem and is getting just as hot even though it was running fine when i first tested it. I have ruled out all possible causes like ventilation, cooler, thermal paste, dust, voltage, reset and updated the bios and so on. I just want to use my PC without having to fear it going up in flames all of a sudden. If anybody has some ideas about the cause if would greatly be appreciated.
Did you check your CPU with Intel Processor Diagnostic Tool? If not, please do it: https://downloadcenter.intel.com/download/19792/Intel-Processor-Diagnostic-Tool