I’ve been having a lot of trouble streaming video on my MacBook Air recently. No matter which site I’m on, YouTube, Hulu, or Netflix, within a few minutes the video becomes choppy and unwatchable. Fed up with my computer’s inability to complete a task it should […]

I’ve been having a lot of trouble streaming video on my MacBook Air recently. No matter which site I’m on, YouTube, Hulu, or Netflix, within a few minutes the video becomes choppy and unwatchable. Fed up with my computer’s inability to complete a task it should be able to handle no problem, I brought her into the Apple store on 14th street in NYC to get repaired…which did not happen.

After I described my problem, and offered up screenshots of the activity monitor showing one of my cores shut down with just Firefox or Safari open, the “genius” looked a my computer for a total of about five minutes before informing me that MacBook Airs were built to be ultraportable and therefore cannot do everything a regular MacBook can, like watch YouTube videos. I was steaming…

After leaving the Apple store, I went home and did some research, where I uncovered the magic pill for the MacBook Air overheating problem, Coolbook. Coolbook is a $10 program that lets you change the frequency and voltage of your processor to reduce heat and fan noise, and increase battery life. Before I found Coolbook I was honestly going to sell my MacBook Air and get a new laptop, but now that I have Coolbook installed and tweaked, my computer is running perfectly.

A Few Notes About Coolbook

  • There is a free version, but it doesn’t let you do anything. Don’t waste your time with it; purchase the full version immediately.
  • The directions are a little confusing, so I’ve outlined some pointers below.
  • There is a whole forum thread about Coolbook here.
  • Although I used it on a MacBook Air to fix my video issues, it should improve the performance of any Mac laptop.
  • I had an email conversation with the developer, so a lot of the information listed is “straight from the horse’s mouth.” Thanks for helping, Magnus!

After you download and purchase Coolbook, go ahead and register it. Once it’s registered you can start to configure it.

Setting a Voltage With Frequency

When you’re configuring frequencies, it’s important to uncheck the “Throttle Active” checkbox.

  1. Select the frequency from the drop-down box
  2. Select the voltage from the drop-down box
  3. Click the set button.

“The lower voltage you can use, the more power you will save. Finding the limits of your CPU requires some experimentation. If you try to step down the voltage one notch at the time, you will eventually reach the limit of your CPU, and you will have a kernel panic (showing the picture of the power button).”

We need to do this process with each frequency for both adapter and battery mode, making sure we save our work each time we find the correct voltage for a frequency.

Throttling Level & Temp Limit

Throttling level controls how easy CoolBook will step up in frequency. A higher value will make the frequency step up quicker, and at a lower CPU load. High is recommended when using temp limit. When the temp limit is reached, CoolBook will step down to a lower frequency in the list. This is done to reduce heat. This feature is not needed for all computer models, but it is recommended on computers that reaches too high temperatures during load.

Throttling Active & Coolbook Active

Finally, it’s time to turn on throttling and Coolbook. Check both boxes and let your system reboot when prompted. When your system is rebooted, it will be running Coolbook in the background. You do not need to launch the application.

Screenshots of My Configuration

Each processor is different, but this is how my system is configured.



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  1. This is all useful information if you are one of the tiny minority of people that have trouble with overheating on the MacBook Air, but I don’t see how a story of your personal troubles with this problem is really something of interest to many.

    I know dozens of people who have MacBook Airs and have serviced and set up a few of them and I have never found anyone that ever had a problem like you describe. My partner uses one as her main computer all day every day since the day it came out and she never had problems either.

    As a tech support person, I would never recommend anyone doing what you are doing to their laptop (using a third party program to futz with the processor). If you really do have this problem and aren’t just inadvertently blocking your air ports or something, I would take the thing back, get your money back and go with a different model.

    1. Gazoobee, I am also a Tech Support person for PC’s. Try Running a Mac book Air Streaming video on netflix or Hulu. This information is important and helpful for someone who would like the processor work using both cores without the computer shutting off. If your friends are playing hearts all day, or browsing the web than you shouldn’t have any problems. And as said before Apple does know about the problem. Don’t put down someone for sharing there experience and presume others do not have this issue as well. May be a large group of people who do not use there computers to there cababilities have no problem. This is what makes the article relevant for those of us who do and don’t know what to do. Isn’t that the point of these forums to help???

    2. This comment makes no sense to me – his story is very interesting and provides background on why he is doing what he is doing.

      Messing with such settings is not for faint hearted and coolbook is for sane people.

    3. Gazoobee,

      Every Macbook Air user I know has this problem.

      How much did Apple pay you for your crude post?

    4. I sometimes have the same problem- and the “genius” at the apple store also told me that the “MacBook Airs were built to be ultraportable and therefore cannot do everything a regular MacBook can”. I was fine with that- I build PCs and have a quad-core work station overclocked to 4ghz on liquid cooling at 28 degrees C with a EVGA GTX 285 2gb super super clocked version for graphics processing. I do my gaming, video encoding, Phys X rendering on that rig. So I don’t need another powerful computer- I bought my Air for music, word documents, and internet browsing. The Mac Air does run hot and the video does sometimes get a little choppy half way through viewing a video.
      As a hardware enthusiast and high end desktop builder, I am encouraging people to use a third party program to “futz” with their processor. Although it can be very dangerous especially with a Macbook Air, if done properly it can save $400 by overclocking the CPU to the $1799 specifications of the Macbook Air.
      The only reason why I would say overclocking a macbook is dangerous is because it is extremely non versatile. One cannot install aftermarket cooling to properly dissipate heat output caused by the increased voltage and increased frequency of the CPU. The only thing that makes me comfortable with overclocking a macbook Air is the body is aluminum- it is very heat conductive- and can dissipate heat from the CPU to the case.
      SO I am more than happy to try and overclock or underclock my macbook Air to get the best performance out of it.
      I do recommend however, that anyone trying to should brush up on how to do it, the dangers of doing it, and the benefits of overclocking.

    5. Gazoobee- You are a fool. Everyone who has a MBA has issues with it overheating, apparently your partner is the one in the “minority.” For those of us with the earlier model like myself, it’s especially troubling- as my warranty has expired, AND I cannot return the thing (that I purchased for 2K … when the dollar was a lot stronger). Whether or not you are a tech person matters not when you are expressing an opinion with little evidence, my friend. Setting up someones brand new computer would not give you any indication of this problem.

      For the rest of you- the “condition” worsens with age- so anyone who can take advantage of a warranty or return their computer- DO SO. I cannot run mine for more than 10 minutes at a time without having to close it, and turn it upside-down to cool off. Well, I must go- as my screen is freezing up now….

    6. CoolBook did eventually fix my issue. I have an external Cinema display and found that whenever I used it on my MacBook Air (1.8 GHz Gen 1) the kernal_task when to 150%+. This made my set-up unusable.
      The solution was CoolBook 2.16.
      My original attempts to install failed and for a long time it made no difference. I then de-installed and re-installed v2.16 and this worked.
      I am using two frequencies 1200 MHz with 0.9v and 1800 MHz with 0.95v and a low Throttling level.
      With this on (and it needs to run all the time – I have it set-up to run on login with hide) the MacBook Air settles at around 55-60 degrees C and the kernal_task never ramps up. I also modied by basic fan speed to 4000rpm (using SMCFanControl). This helped as well.
      The install of CoolBook is a disaster, but keep trying. Eventually it works and this makes the MacBook Air useable.

    7. I’ve had this problem forever, 1Gen MBA SSD, I am trying out this program now, thanks for the write-up

  2. Roger Bourland Wednesday, April 15, 2009

    i had the same problem with my macbook pro and finally solved it by unplugging th power cord on my airport and then plugging it back in after a minute or so. it was driving me crazy. no problem since!


  3. @Gazoobee The first part of the story is about me going to the Apple store to get help, but they admitted it’s a known problem with the machines, and that they would not repair or replace it. Overheating is a known and documented issue with the Airs. Also, this software cannot harm your computer, in fact it makes it run cooler and last longer…

  4. It’s likely this has nothing to do with the Macbook Air – I have the same problem with streaming video on both my MBPro and MB. It’s a known issue with streaming flash video on OS X, and is documented around the web, notably here:


    The fix I’ve seen is to go into your Flash properties and disable hardware acceleration.

    1. Thanks Staticred.. it worked for me. the videos and games are not choppy anymore but it did not solve the heating problem.

  5. @ Jenny:

    Sorry, I wasn’t trying to be too critical, I know this is a big issue for those that have it, just that the number of people that have this is so small I was wondering if yet another big article on it was worthwhile. I’ve read sooo much about this but never actually seen it or know of anyone that has been affected by it as I said.

    I do like the fact that your explanation of using the shareware product is detailed and thorough because I still disagree that you “cannot harm your computer” with it. It’s possible.

    1. Yeah, I know it has been a year….

      anyhow, Gazoobee, still seems to be reluctant to admit that this is a huge issue. A small number of people??? Why is the internet full of posts about this problem? I guess you he works for Apple or something.

      Anyway I am having the same problem with my MBA. Only watching streaming video heats up my MBA like crazy, and the video becomes like a slide show. This should not be a problem for a nifty and very costly laptop.

      I have done some overclocking on PC’s, so I think I’ll give this a try too. At first I thought I was reading an advertorial… but it seems pretty legit. 10$ wouldn’t hurt that much

    2. Well since THEPRUTSEE replied after a year, I might as well too (since I stumbled upon this after searching for “Macbook overheats”. I agree that a lot people watch streaming video (Youtube, Netflix, ITunes TV/movies) for more than 15 minutes at the time and @GAZOOBEE is being pretty dismissive and snobby in his reply… very similar to Apple’s “you’re holding the phone wrong” response.

      Now I want to make it clear that I the Macbook Air is a great device for what it was designed for and I think overall the iPhone 4 is a nice phone (I don’t actually own one – I actually have a Sprint Evo 4G which has it’s own issues, but I can appreciate good design). They have issues and some people can live with the issues, and some people cannot. I just think that GAZOBEE is condescending in his dismissal for what appears to me to be a valid issue to some people.

  6. The reason I use a Mac is exactly so I don’t have to deal with crap like this.

  7. Sounds like the genius works for Microsoft. OR a tech person in India that is 3 pages ahead of you in a book Microsoft does not sell

    1. I wouldn’t go India bashing that fast – I’ve got quite a few friends from India who are extremely intelligible.

  8. Good article – this app is very useful for those ‘in the know’ to get the best performance from their Mac investment. RMClock is the free alternative for Windows users (or boot camped Macs) I’d wish Coolbook authors would put a fully functioning time-limited version out so we could better determine it’s benefits before purchasing?

  9. Slightly essential bit of info missing here? Is this a Rev A or Rev B MBA? The Rev A is known for shutting down its cores and wheezing when it gets a bit warm. I’ve found my Rev B to be mostly hunky dory.

  10. Never had any problem with my (Rev A) MBA, but with other Macs, the free smcFanControl (GPL, donations* are welcome) has always been enought for me to solve all overheating problems.


    *: to the author, not to me… unless you insist ;)

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