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I recently got a laptop with a 4 core (8 thread) Intel i7 CPU, running Windows. Unless I'm really pushing it, it doesn't heat up very much. However when I installed Linux it began to heat up significantly and battery life got much shorter. Specifically a this is a Debian-based live CD of Tails booted with toram so the disc is not inserted and the root filesystem is a squashfs image living in memory.

I'm aware that Windows has some power optimizations for power usage that Linux doesn't use by default, but here's where it gets weird:

  • I disabled the discrete graphics chip by booting with nouveau.modeset=0.
  • I disabled SMP, so the system is running only a single physical core.
  • I used cpufreq-set to reduce the maximum clock rate to 800 MHz.

Despite all this, the laptop is getting really hot. If I leave it idling for an hour (CPU usage typically around 1% the entire time), it gets so hot that my kernel log starts accumulating overheating errors, saying that the CPU clock had to be throttled (it's already at its minimum and can't go any lower).

What in the world could be causing so much heat when I run Linux? How could a Windows system with 4 cores running at an average of 1.5 to 3 GHz at any given time and running the discrete GPU generate significantly less heat than a Linux system with a single enabled core running at 0.8 GHz?

The current output of sensors shows that the CPU itself isn't that hot:

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +65.0°C  (high = +86.0°C, crit = +100.0°C)
Core 0:        +64.0°C  (high = +86.0°C, crit = +100.0°C)

thinkpad-isa-0000
Adapter: ISA adapter
fan1:        2880 RPM

The fan is under the control of the laptop's EC.

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  • “Specifically a Debian-based live CD…” So did you actually install a real Linux install off of this CD? Or did you simply clone a live CD to the machine? May 30, 2019 at 23:58
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    @JakeGould It's Tails, a live Debian system. It was booted with toram so the disc is not inserted. The root filesystem is a squashfs image living in memory.
    – forest
    May 31, 2019 at 0:05
  • This seems like it might be a very specific issue with Tails. Have you seen this? May 31, 2019 at 0:16
  • @JakeGould I strongly doubt it. Tails is barely changed from regular Debian Live. Anyway, if it was, it would most likely be the result of some program getting stuck in a loop and eating up the CPU. That means it's a kernel issue, and Tails does not use a custom kernel. I'm confident that it's not Tails-specific.
    – forest
    May 31, 2019 at 0:20
  • Maybe it is a Tails specific issue in the sense that it doesn't benefit from tweaks and specific firmwares that other distros that are meant to be installed and have repositories, etc.
    – user931000
    May 31, 2019 at 2:25

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