That's because you are looking at the wrong readings... The critical temperature is the GPU. You can get it with this command:
Code:
sensors | grep TG0d
Under OS X, the radeon card runs around 50 ° C, often lower. In vanilla Ubuntu, temperature goes up into the high 60s, on hot days or when you're doing graphics intensive things into the high 70s. Now some people say that's quite OK and well within the specs of the radeon cards, but the back of the aluminum display feels really hot, and I'm not comfortable with it. After doing some reading on the net, it turns out that the culprit is the open source radeon driver. It doesn't have any power management and always runs the card at maximum performance, which of course makes it hot. It appears that linux kernel 3.11, which is currently under development, will include a whole series of patches which will allow radeon power management (more info
in this phoronix article). So what can you do if you don't want these high temperatures? I see three possibilities:
- Install a 3.11 kernel and try the power management described in the article linked above. A bit convoluted right now because the kernel is still in development, you will have to download the source, apply patches and compile the kernel.
- Switch to the proprietary drivers (ati fglrx). I have tried this, and it brings the temperature to the same levels as under OS X. The catch: I haven't had any luck with Ubuntu's driver utility (it's called "jockey," I think); I had to download the zip of the latest version from the amd website and install it manually. And this is something you will have to repeat whenever Ubuntu pushes a new kernel version into the updates.
- You can force the open source driver to run with a lower power profile. Just run these commands:
Code:
sudo su
<enter your password>
echo "mid" > /sys/class/drm/card0/device/power_profile
This will make your card run with the predefined "mid" profile. It lowers graphics performance quite a bit (so switching applications via Alt-Tab may be sluggish), but it brings the temperature down to reasonable levels.
For the time being, I use method 3, especially on hot days (as we have had this month in Europe), but I hope saucy includes the 3.11 kernel and the new power management utilities.
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