Background of the issue.
New system shipped from factory, even as recent as May 2017 are suffering from extreme core differential problem even at stock speed. True the problem is a little bit better now with the Kaby lake models, but it is still there and wide spread. I must say, over 80% of the systems being shipped came with this problem, if not all.
How to detect this issue.
Easy. Run a CPU stress program like OCCT or wPRIME and monitor your CPU temperature. If all 4 CPU cores are within 3-5C degrees (example: 75C, 76C, 74C, 77C), you are one of the very few lucky ones. If 2 of your CPU cores are 10C+ hotter than the other 2 cores (example: 80C, 90C, 82C, 92C), your system is suffering from this issue. note that the core differential problem always come in pairs. Core 0, 2, or Core 1, 3 depending on which area on the CPU die has less contact with the heatsink. The problem is also AMPLIFIED significantly for those who OC their 6820HK/7820HK CPU without undervolt. In the earlier batch of skylake systems, the temperature difference can be over 20C easily!
Cause of the problem.
The heatsink of the CPU is not making proper contact with the CPU die surface. Especially the first half upper region of the CPU. This is due to the heatsink of the CPU resting at an angle (when viewed sideways) on the CPU die surface due to 2 main problems.
1. Poor CPU tripod tension arm design, weakest point at the single arm top part of the CPU. not providing enough pressure to allow the CPU heatsink to sit flush with the CPU die.
2. Thermal pads. use of thermal pads thicker than you should on the power delivery components on top of the CPU raised the heatsink up at the top side and the already weak cpu tension arm does not help at all. the initial skylake models were even worse using thick thermal pads on the larger silver chokes which were rectified later with the very thin white pads. This enhancement was done in part due to iunlock & Team LHz holding discussion with dell engineering team. the CPU core temperature differential reduced from over 20C to 10C.
