Posts Tagged ‘Fan Control’

exponent for Fan Control

Friday, January 2nd, 2009

Here’s another patch for some third party software, this time for keeping your intel mac CPU cool.

I’ve been using Lobotomo’s Fan Control preference pane and daemon to control scud’s fan speeds since I installed OS X.

It’s useful because it means you can idle with quieter fans in a cool environment, but still have them rev up to max before you burn your fingers. However, one thing that’s annoyed me for a while is that you only really control the floor and ceiling thresholds of a linear response curve.

In my experience (engineers or physicists can correct me), at a constant CPU load, there are multiple equilibrium temperature/fan-speed combinations, but they’re not collinear. In the original Fan Control, the response curve is linear. Taking a hint from gamma correction, I have patched Fan Control 1.2 to use an exponential curve. Where T is the temperature, the target fan speed F is governed by the equation:

F_b + (F_m - F_b) ((T - T_l)/(T_b - T_l))^γ

I also reduced the minimum upper threshold temperature to 60˚C.

You can browse the source in git or download the binary installer. I’ve only tested on scud (running Leopard). Feedback is welcome as comments here on the blog.

Screenshot

exponential curve screenshot

Of course, there may be more effective measures to combat a hot macbook pro.