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Recently I have noticed that a game that used to run at a constant 60 fps on my pc is not doing so anymore, I haven't played a game for a while but ran this game (batman arkham knight) for my nephew and noticed severe lag and frame drops, then I tried another game (assassin's creed origins) which used to run at almost 60 fps and now it is not exceeding 23 fps.

So I started investigating and after a little while I noticed that my cpu is idling at a temp between 100 C - 105 C (yes, Celsius) through msi after burner , I tried "open hardware monitor" and it is reporting the same temps, I rebooted into bios and it is showing constant 96 C.

The cpu is also underclocking itself because of these false reading, how am I sure these are false reading you may ask .. well I went into the extreme and started up my pc without the cpu fan (it is the stock intel fan) attached to the cpu and booted into bios and it is still showing 96 C, while it is showing this, a temp reading from my temperature reading gun (and pointed directly to the cpu) is showing temps between 55C - 65C (reasonable temps since there is no fan at all) so I am really suspecting there is something wrong with temp sensors..

Here is my specs for the record:

  • intel core i7 3770
  • gigabyte ga-h61m-s2p mobo (with latest bios)
  • 16 gb ram
  • msi gaming x gtx 1060 6gb ram
  • evga 500w 80+

Another thing to mention is that there hasn't been a single crash/shutdown/bsod even when I ran the games, just underclocking.

So what would be the problem ? Could it be that the cpu temp sensor has gone bad?

  • If you started up a modern CPU without active cooling, the fan, there's a good chance you fully or partially damaged it and it may not be apparent right away. – headkase Nov 2 '18 at 10:39
  • But what about the false temperature readings? They were wrong even before i started it without the fan. – Abdurrhman Nov 2 '18 at 10:47
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    Temperature guns measure an area not a specific point so they are only accurate for large homogenous areas. At about 30cm the area being measured is probably larger than your CPU and is an average of that large area, not a specific point on you CPU. The laser pointer is also often slightly above the area being measured. You probably need to replace the thermal paste and/or the CPU fan. I doubt your temperature sensors are wrong. – Mokubai Nov 2 '18 at 11:06
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    If you want an accurate temperature measurement then you should use a thermocouple or contact thermometer. – Mokubai Nov 2 '18 at 11:09
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It is possible for this sensor to go bad, although this is somewhat rare.

Just lately I have answered a similar question in the post CPU Does not run at full speed, where no reasonable alternative was found, except for installing the free ThrottleStop which blocks the CPU from throttling. This solution is only to be used if you are absolutely sure that these readings are false.

This solution is much better than replacing the motherboard, except if your computer is still under warranty that can be activated for the repair or exchange of the motherboard.

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  • thank you harrymc very much for your effort, it turned out to be incorrectly installed fan (which is weird because i already adjusted it before posting my question but looks like it wasn't 100% tight) anyways thank you for your reply. – Abdurrhman Nov 2 '18 at 17:43
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thankfully the problem is now solved and what i did was remove the cpu (the fan was already removed), clean the dust off the edges of the cpu (unfortunately i could't remove the thermal paste because i don't have any at the moment, but will buy soon and replace it), reinstalled the cpu and this time i made sure the fan is installed 100% correctly.

i booted the pc and waited till everything settle down, and the cpu was idling at 41 C and went up to 60 C while playing assassins creed origins, and yes it is running at constant 60 fps again.

looks like the fan was a little bit loose even though i removed it and reinstalled it before posting the question.

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Firstly PIR-sensor based temperature guns measure an area not a specific point so they are only accurate for large homogenous areas. At about 30cm the area being measured is probably larger than your CPU and is an average of that large area, not a specific point on you CPU.

The laser pointer is also often slightly above the area being measured. Thus the reading of "about 65 degrees" is questionable and probably significantly lower than the centre point of the CPU case where your CPU die makes contact with the heat spreader.

In order to make an accurate temperature measurement you should use a thermocouple probe with a small point and press it at the centre of your CPU heat spreader.

You probably need to replace the thermal paste and/or the CPU fan. I doubt your temperature sensors are wrong.

I have seen rare cases where the CPU heat spreader has become detached from the actual CPU die and necessitated removal of the spreader, though this is a dangerous task and I would not recommend trying it at home. Refitting a fan to a naked CPU die is possible but you increase the risk of serious damage to the CPU.

  • thank you so much Mokubai for the information you provided, i have solved the issue by removing the cpu and giving it a little clean and reinstalling it and made sure the fan is installed 100% correctly. – Abdurrhman Nov 2 '18 at 17:40

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