So I have a machine which has both latest *Ubuntu and Windows 8 on it. On windows 8 my CPU temp is roughtly 26 degrees when idle. Now when I boot into Ubuntu, CPU temperature is suddenly 43 degrees when idle, plus my fans are making a lot of noise which is probably because of the CPU degrees.

Why is that? Everywhere I read it says the Linux is much better at managing CPU and so on. But yet it seems something is wrong.

It is a stock installation of Ubuntu 14.04 and my CPU is a Intel i5-4570

  • Have you ever tried checking inside the box to see if the CPU is actually hot? I recently replaced my motherboard... the first one I got was an AMD MSI that read overly high both in the BIOS and Ubuntu (I don't have Windows). But that motherboard had a sound problem, so I replaced it with a similar Asus, which read much lower in the BIOS, and gave higher, but wildly fluctuating readings in Ubuntu. In both cases, though, the CPU barely felt warm, and the heatsink was not warm, not was the area around the CPU. But the fan seemed OK. – Marty Fried May 26 '14 at 21:00
  • I dont have much to measure the temp with sadly. I doupt that I would feel much difference with my fingers. But the fans are on a higher RPM too on Ubuntu and I do think it's because of the temp. – Kaspar May 26 '14 at 21:01
  • I think it is your GPU to make your CPU warmer. You said that you're using a stock installation, so you didn't install any proprietary driver for your GPU, right? Try installing the right driver for your GPU from Software Sources. It should make the system cooler. – nastys May 26 '14 at 21:50
  • Well I tried both the latest Nvidia driver 337 I think it was and the one that Ubuntu suggests which is a bit older. Both are not changing much. Also my GPU seems to be the only piece that is at the same temp on idle as it is on Windows. – Kaspar May 26 '14 at 22:09
  • Is this a laptop with AMD GPU? – psusi May 26 '14 at 23:48

Ubuntu come configured to use the CPU in its limit when it is needed. You can configure your computer to use less processing power than it is available and things will cool down.

Open a terminal and type:

sudo nano /etc/rc.local

add this lines before the exit(0)

for i in `ls /sys/bus/cpu/devices/ | egrep "^cpu[0-9]+"`; do echo "2000000" > /sys/bus/cpu/devices/$i/cpufreq/scaling_max_freq; done
sysctl -w vm.swappiness=0

and then reboot your computer or execute this command:

sudo /etc/rc.local

This will make your computer a little slower, a lot colder and your battery time will increase.

Tweak a bit with the frequency. You can see the valid frequencies with this command:

cat /sys/bus/cpu/devices/cpu0/cpufreq/scaling_available_frequencies

On my i5-3230M valid values are: 2601000 2600000 2500000 2400000 2300000 2200000 2100000 2000000 1900000 1800000 1700000 1600000 1500000 1400000 1300000 1200000. But you should have more high frequencies available.

Most of the time I limit to the minumum frequency (12000000) and still have a very good desktop experience on ubuntu gnome. I use ubuntu gnome 3 desktop, lots of openoffice, google sketchup and eclipse. I draw a lot.

  • That is only going to help if you make a habit of running badly behaving programs that waste all the cpu time they can get without actually doing much. Otherwise the cpu frequency is automatically lowered when nothing needs it ( and in fact, when idle, modern Intel cpus are actually powered down ). – psusi May 26 '14 at 23:52
  • yes, psusi, when the computer is idle makes little difference to me (as you pointed out). Make difference when I am using it. Even in low frequencies I can watch youtube on full hd, compile java programs, train neural networks and decision trees, draw in libreoffice and sketch. My notebook remains cool and the speed is enought to me. – Lucas May 29 '14 at 3:48

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