Fan speed on Macbook Pro

Two days ago I finally spent some time to fix my MRTG installation that had been broken by a Perl upgrade half a year ago. As you can see from the graph below, it would take another day before I decided to fix the fan speed probe for my Macbook on Ubuntu.

Another day later I rebooted back into MacOS X. I was going to write a script to return the fan speed data, but found a probe I had already written from three years ago. Miraculously, the script actually still worked. All that was missing was to make my Macbook respond to MRTG’s queries.

When all the dust settled this is what I got:

What’s interesting is that in Ubuntu, the fan speed fluctuated between about 2500 and 6000 rpm (rarely going over 4500); however, on MacOS X it pretty much stayed constant around 6000 rpm.

What does this mean?

About a year after I got my current Macbook I ran into overheating problems and wrote a script to monitor the computer’s temperature and ramp up the fan speed if it looks too warm. As can be seen from the graph, the fan is on max speed almost 100% of the time; yet I still run into overheating problems from time to time.

On Ubuntu I ran macfanctld with somewhat more aggressive settings than the default. Yet when the computer is idle fan speed actually ramps down near 2500 rpm.

I do run into overheating problems also on Ubuntu, but it’s not any more frequent than what I get on MacOS X. However, if I run the fan slower on MacOS X I actually run into problems more often.

So MacOS X seems to run hotter than Linux. Strangely, battery life sucks on Ubuntu so MacOS X actually seems to require less power to run. Why this is so is a mystery.