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I am a bit confused about how does sensors command work?

My CPU Model is Intel(R) Core(TM) i7-4720HQ CPU @ 2.60GHz

When I turn on my laptop it shows me avg 50 degrees centigrade temperature, If I build a project in Android studio it elevates to 80+ instantly and when the build is completed it again falls down to 50 instantly? How's it possible so rapid rise and fall of temperature within almost a second?

Does it show the exact temperature or it guesses according to running processes?

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  • What processor make and model? do grep "model name" /proc/cpuinfo. If I were to guess, I would say that you have a poor thermal bond between your processor and its heat sink. Jul 28 '20 at 22:36
  • I have edited my question. Jul 29 '20 at 3:06
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You did not mention which temperature, but assuming you mean the processor temperature of one of its cores or the package:

Yes, absolutely the temperature can rise and fall that fast. Rate is a function of cooling method and how good a thermal bond you have between your processor and that cooling method.

Passive cooling methods require some temperature differential for heat to flow from hot to cold. The higher the differential the faster the heat flow.

Liquid cooling methods bring the cold to very close proximity to the processor itself, requiring very little temperature differential for good heat flow.

As far as I know sensors does not guess.

Here is an example using an air cooled Intel i7-2600K processor, with known good thermal bond between the processor and the heat sink and known fast fan response time. Using turbostat instead of lm-sensors, and prime95 torture test to create high heat load:

$ sudo turbostat --Summary --quiet --show Busy%,Bzy_MHz,PkgTmp,PkgWatt,GFXWatt,IRQ --interval 0.25
Busy%   Bzy_MHz IRQ     PkgTmp  PkgWatt GFXWatt
0.16    2029    61      37      4.16    0.12
0.14    1872    57      37      4.10    0.12
0.13    1932    60      39      4.11    0.12
52.09   3498    1251    54      47.29   0.12 <<< load applied, already 15 degress
100.00  3500    2063    58      87.15   0.12
100.00  3500    2058    60      87.55   0.12
100.00  3500    2054    62      88.07   0.12
100.00  3500    2064    63      87.96   0.12
100.00  3500    2052    64      88.29   0.12
100.00  3500    2067    64      88.12   0.12
100.00  3500    2053    64      88.13   0.12
100.00  3500    2063    65      88.30   0.12
100.00  3500    2060    66      88.56   0.12
100.00  3500    2058    65      88.35   0.12
100.00  3500    2057    65      88.30   0.12
100.00  3500    2058    66      88.78   0.12
100.00  3500    2055    66      88.40   0.12
100.00  3500    2060    67      88.56   0.12
100.00  3500    2053    67      88.84   0.12
100.00  3500    2062    67      88.57   0.12
100.00  3500    2056    67      88.56   0.12
99.99   3164    2074    62      76.39   0.12 <<< Throttling
100.00  2700    2052    61      58.25   0.12
100.00  2700    2063    60      58.34   0.12
100.00  2700    2063    60      58.14   0.12

So, sampling at 4 hertz (0.25 seconds period) we saw 52% after the load was applied, therefore we know it was roughly 1/2 way between samples. So the processor temperature went up 15 degrees in approximately 0.125 seconds.

To protect my processor for this experiment, I also ran thermald with a low trip point, and you can observe it throttling the CPU frequency after awhile.

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  • Thanks for such a detailed and informative answer. I just have a last query, either 50 degrees a normal temperature for Intel(R) Core(TM) i7-4720HQ CPU @ 2.60GHz or I need to do something else as I just changed thermal paste about a week ago. Jul 29 '20 at 3:16
  • 50 does seems a little high, but it depends on how "idle" your LapTop really is. I am a server person, and my test servers really are quite "idle". You also probably have a GPU adding to the waste heat issue. By the way, turbostat (linux-tools common package, I think) will work with your processor. I haven't used lm-sensors for many years now. Jul 29 '20 at 3:26

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