Tips, tricks and traps

MacBook Air Core Shutdowns and Freezes

Well, maybe I’m hard on hardware, but have four problems with my MacBook Air right now in order of problems:

h2. “Intermittent Freezing”:http://discussions.apple.com/thread.jspa?threadID=1415343&tstart=0 (aka “Core Shutdown”:http://discussions.apple.com/thread.jspa?threadID=1445521&tstart=1)

Originally I thought that this was because my hard disk has corruption problems. ClamAV would run and then system would lock, so then I disabled this, but still had it. Then had to repair the disk which was complicated (see below the SuperDrive problem) but finally fixed that.

The main issue looks like when the MacBook Air gets really hot when you are watching a video, the system freezes for 10-15 seconds and then starts. I have the same symptoms which is one core looks like it is at zero and the other is maxed out. For a while I thought it was something in the background and I do see kernel task (whatever that is maxing out). You can get this quite easily by playing a Youtube video and playing a movie in itunes for about 10 minutes.

Some folks think that is has to do with using it on your lap and not a hard surface because it covers the vents in the back. Apple actually recommends that you don’t operate it with a pillow or on your lap. (Funny, I don’t think they are super realistic about that!)

Most folks are using “istats”:http://www.islayer.com/ to check the CPU temperatures that are up to 90C! “Macsimumnews.com”:http://www.macsimumnews.com/index.php/archive/macosg_macbook_airs_intermittently_freezing has a good summary.

Some people are having success with resetting the SMC (system management controller) by. The current theory is that when you get to a certain heat level, instead of lower clock frequency, one of the cores shuts down and you get a full freeze. One guy actually cracked his MBA and redid the thermal grease on his system. Other have installed something called “smcFanControl”: which spins the fan at the 6200rpm macx all the time.

Others thing that it is a heatsink failure so you need to take to the Apple Store to replace. Other report that installing the “SMC Update”:http://www.apple.com/support/downloads/macbookairsmcupdate10.html fixes it although it you’ve been taking all the Apple Updates you should be up to 1.23f9, Start /Utilities/System Profiler to see what version SMC you have

# Shutdown the Mac
# Hold shift+control+option+power on
# wait 5 seconds (no chord of heaven)
# power on

Other like “Paul Stamatiou”:http://paulstamatiou.com/2008/05/11/putting-an-end-to-macbook-air-core-shutdown say that this happens with lots of graphics like watching a movie because the GPU and the CPU share the same heat sink. That’s true, with my MBA, it happens often when watching a movie. His solution is undervolting with a third party app called “Coolbook”:http://www.coolbook.se/CoolBook.html. You use the parameters that “Plasmadesign.com”:http://plasmadesign.wordpress.com/2008/04/02/macbook-air-core-shutdown/ suggests which are essentially keeping it at 0.9V under 1.6GHz and at 0.95V at 1.6Ghz. This is much lower than the stock 1.1V. In battery mode, it is 0.9V and you only run it at 1.2GHz under battery power. BTW, this also increases battery life significantly too, although the machine is obviously much slower.

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