It appears the fan may not be cooling the units properly, causing random lockups that render the MacBook Air unresponsive for 10 to 15 seconds, or longer. Under load, despite the fan running wide open, the internal temps can get so high, that the processor core(s) temporarily shut down and cause the intermittent freezes. The problem can even be exacerbated when running the Air in warn environmental temperatures.
Deny Dias over at Apple Discussions describes what happens to his MacBook Air:
1 - Turn it on
2 - Log in
3 - Open Safari (or Firefox, whatever)
4 - Open a YouTube video
5 - Play (and wait) for five minutes
6 - Frezze > 10s > Unfreeze > 10s > Freeze.
"After I watch around 4 minutes of any YouTube content, the behavior starts to show up. The "magic" number seems to be around the 163º F (73º C). When MBA goes beyond this temperature, the CPU bar graph of Activity Monitor shows a slow down on core #2 (right one on the graph) while the core #1 raises up to the top. A this moment, the system starts to glitch. After a few seconds (2 or 3), the core #2 goes back get to work, the core #1 slows down and the system resume its normal operations. If you let it playing the video for another half minute, the temperature keep raising to 167º F (75º C) and them it freeze. After that, you have 10 seconds of a working system, then 10 seconds of total freeze and so on, but only with core #1 while core #2 seems to be shut off. If you then pause the video, in about 3 minutes everything get back to its normality."
"During the above test, the fan started at around 2500 rpm and after the video started to play, it reached 6220 rpm. Even after I stopped the video it kept running that fast. Now I'm 131º F (55º C) and it still runing at 6200 rpm. The temperature top was 178ºF (81º C). Things seem a bit worst to me because I'm in Brazil, São Paulo. This means 86º F on a ordinary day."
donluca writes, "Thanks to the XCode developer's extras, I managed to shut down one of the two cores and guess what? With only one core enabled it stutters, no matter if it's hot or cold. So this is my theory: When the heat reaches a certain limit, instead of lowering the frequencies, it disables one core and we have the intermittent freezing problem. In fact I tried using Windows XP through boot camp, and no matter what I did, it never froze. My opinion is that the problem is OS and/or driver related and I think it will be fixed in the future with a patch."
This week, Apple released a MacBook Air SMC Update that fine tunes the speed and operation of the internal fan. The SMC Update is supposed to address the problem, but some owners are reporting that when running the update, it reports that the update is already installed, and they continue to have problems.
You can follow the progress of the problem via the following links at Apple Discussions:
Topic : Macbook Air intermittent freezing problem
Topic : MacBook Air Fan Running Constantly
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