Undervolting the Macbook Air

After reading this post about running cooler without losing performance from the MacRumors forums, I decided I would also try to undervolt my Macbook Air.

What is Undervolting
Undervolting is different from underclocking. Undervolting is a software-based tweak to decrease the amount of power being sent to your CPU. CPUs are not consistent in the amount of voltage needed. Since laptops are mass-produced, they just set a high threshold to ensure the stability of every laptop. On most laptops and in particular the Macbook Air, the voltage is set a lot higher than that which is necessary on the actual chip you received. Undervolting will not reduce the performance of your laptop. Some people claim that it can even speed up the performance of your laptop if it runs at a more optimal temperature without needing to turn on your fan as often, but I think this is purely theoretical and if it does, the performance difference would be marginal at best.

How to Undervolt
Using CoolBook, a Mac-only software by Magnus Lundholm, I was able to play with the settings on my laptop. It also works on Macbooks and Macbook Pros. Depending on how hot your computer gets, it will run at different clock speeds. You can adjust the number of volts sent to the CPU at each speed, or remove different speeds from the configuration. Removing slower speeds will have your computer run faster even if it's getting hot. Removing faster speeds will help conserve energy, particularly useful when you are stuck being on battery power for a long time. The settings are easily resettable to the default, so you don't have to worry about not being able to put your laptop back to the way it was if you are not happy with it.

Since each CPU differs, I cannot recommend a certain set of voltages that will work for your particular laptop, even if it's a Macbook Air like mine. You just have to play with the settings. You can use CPUTest to check your settings to make sure that it works. It'll be some guess and check, but you don't have to tweak it exactly to achieve noticeable results. CPUTest is a free download.

My Results
My computer is very noticeably cooler to touch. Before tweaking, a few minutes of use would bring the bottom of my laptop surprisingly hot to touch. After the tweaking, it remains cool to slightly warm always. I have to say though, during sessions of intense use, the fan still runs a lot more than I would like, but it's definitely an improvement. I spent about 20 minutes playing with my settings, so they probably aren't optimal but I am still more than pleased with the results. And I could always go back and retweak the settings.

The only slight hiccup I had in the process was in the purchase of the license. A license for CoolBook does cost $10 USD (+25% VAT in the EU), which I think is a perfectly reasonable price, and can be bought with PayPal. My PayPal account is set-up to send e-Checks, which take a few days to clear. Understandably, I did not get my license until my check cleared, though I didn't receive verification that the transaction was in process until I pinged support. But don't worry, as soon as it cleared I received my license immediately. They were very responsive once pinged.