After reading the forum this thread can be closed.

[_Hertz_]

After reading the forum, similar problems with the 13/14th and Core Ultra series overheating and isolated Cores dropping performance significantly and heavily thermal throttling seens to be a normal behavior in this series.
Thanks in advance.

[JedG_Intel]

Hello _Hertz_,

Thank you for posting on Intel Community Forum.

It seems that you have found the answers to your questions. Could you kindly confirm if we may proceed with closing this thread?

I look forward to your response.

Best regards

Jed G.

Intel Customer Support Technician

[_Hertz_]

Hi Jed G.
I won the lottery, but there was no prize.
My Core Ultra 9 275HX mobile passed all stress tests without failure (XTU/diagnostic tool..etc), getting 1P-Core essentially dead (sensor failure/ISH), with a very significant drop in performance over 1 P-Core and thermal throttling overheating all over the package. During heavy taskts (98C -104C) with CPU/dGPU heavy loads, a massive thermal throttling happens and performace downs dramatically.

All measures have been taken, and there's nothing that can be done. (the notebook was already RMA and came back in the same way it was sent, they made nothing, only bench tests, even I sending video proofs of this one P-Core behavior, another warranty/RMA claim was denied, etc.)
The notebook manufacturer guarantees that the CPU is perfectly fine and will not reapply the thermal interface.
It seens the manufacturer don't follow Intel Profiles, delivering 175W PL1/PL2 and almost 1.3v hard coded by BIOS. (with all updated bios releases) 
Bios it's under an overclock protection that needs to be disable to be accessed for undervolt options, also needing to turn off intel TXT, with an offset protection for just -0.030v for undervoltage. Rendering impossible to use this configuration without voiding the warranty with almost none results for just too little offset. It's a very simple BIOS with almost none configuration to tweak.  

Thank you.
Best regards.
This thread can be closed.

[JedG_Intel]

Hello _Hertz_,

Thank you for providing this information. We sincerely appreciate your efforts in troubleshooting the issue.

As the original equipment manufacturer (OEM) has confirmed that the processor is functioning as expected, we will now proceed to close this inquiry. Should you have any further questions or concerns, please feel free to submit a new request, as this thread will no longer be monitored.

Best regards

Jed G.

Intel Customer Support Technician