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I have a Dell Precision 7550 with an Intel Xeon W-10885M (Comet Lake), and sometimes, on Ubuntu only (not on Windows), my CPU get stuck at 800Mhz when plugged in (no problem on battery). I'm trying to understand what happens, and what triggers this behaviour.

QUESTION: What are all the bits/registers I could try with readmsr to read to understand what happens or what was triggered? How to read them correctly? How to interpret them correctly?

Note: It's unlikely to be a temperature problem, because I checked the temperature with lm-sensors and everything seems fine. I'm looking for the signal/trigger to at least understand where it's coming from.

Vincent
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  • It's a relatively well known issue with various laptops. I'm not sure what's the cause - I have yet to meet someone who knows - but solutions usually involve resetting BIOS to defaults or replacing the motherboard. I've heard of cases where Dell replaced them under warranty. – gronostaj Aug 25 '22 at 15:51
  • Google "BD PROCHOT". It is that signal that locks devices at 800MHz and is often due to the system controller believing that other devices are overheating and not your processor. – Mokubai Aug 25 '22 at 19:21

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