CoolBook on Macbook Air

July 26th, 2008 · No Comments

I recently got a shiny new macbook air and I absolutely love it. However, I noticed that once in a while it would shutdown a core to keep the heat down. I really didn’t like that so I bought CoolBook. The software claims to undervolt your cpu, which is “safe” (read: user be careful). I believe that it does do this and it does say that macbook air support is not fully tested on the site, so I was warned.

After configuring the CoolBook driver to allow my cpu to scale to its full 1800mhz while being undervolted by approx .5v, the driver appeared to work correctly. I am using two applications to monitor my system, MenuMeters and Tempature Monitor. Both provide me with good indicators of cpu load and tempature. Another warning, I am not using a benchmarking tool aside from my observations. This is not the way to compare things!

My basic benchmark was a 5 minute continuous process. In this case gcc builds. Before installing CoolBook or the latest firmware, a cpu core would generally shutdown 2 mintues into the build. The cpu would also run very hot and the fans would rarely, if ever, turn on. However, I never ran into kernel panics.

After installing CoolBook, I was able to build all the software needed, but my CPU would typically reach tempatures of 80c or higher. I believe the OS X kernel will panic at 85c. I attempted to use the CoolBook max tempature feature, but that clearly didn’t work. My CPU would consistently break the limit and set off many alerts. I am also pretty sure that it caused a few kernel panics; disabeling it cut the number significantly. CoolBook also appeared to favor one core over the other and would typically schedule the 1st core to handle the bulk of the load. I am not sure why this scheduling occured, but it was not a good indicator of a properly functioning kernel. Finally, the fan was still unheard from on the Air, not a good sign.

During my CoolBook usage, a firmware update came out for the Air and I installed it, then reloaded CoolBook. The CoolBook software did not work well with this update. The cpu would typically scale to loads of 2.5 or greatly and easily reach the 85c kernel panic tempature. It pretty much rendered the system worthless for longer build cycles. I removed the software and it now schedules both cpu’s evenly and runs about 10c cooler than with CoolBook.

I know the CoolBook developer warns that the Macbook Air is not really supported and that’s all fine. I’m not angry about the software failing, I was warned. I am pretty pissed at all the people who claim CoolBook is a great piece of software on the Air. There are plenty of threads screaming about this (Just google CoolBook+Macbook+Air), and I am pretty sure they’re all users that never actually tested the software. Again, if the main issue for a user is view You Tube, I probably shouldn’t take their advice and I didn’t. Then there is Macworld and Chip Chick, both WRONG and Totally Lame! They should actually test their claims, but I guess not! Also, do either one of your sites use a computer for anything else than rick rolling?

The Bottom Line:

Don’t use CoolBook on your Air. It doesn’t work correctly and will cause kernel panics. Apple’s latest firmaware is pretty good and runs cool. When you’re doing heavy builds, the fan will run. Sorry…
Don’t believe anyone who’s biggest complaint is that they can’t watch You Tube.
Finally, hacking the kernel is a hard and unstable process. It is not a good policy to install kernel mods that you cannot review if they affect the cpu directly.

Well, I certainly learned my lessons. Hope this is helpful. It’s got my interesting in OS X kernel hacking perked so look for more from me on that.