Monday, July 6, 2009

Macbook Air - kernel_task process and overheating

Although here at Go Go we are specialist at both Apple and Windows technology we definitely have a bias towards Apple hardware.

This case is no different for Apple's thin and luxurious Macbook Air.

However, like many Apple designed products some sacrifices are made for aesthetic purposes. In the case of the Macbook Air, things like sufficient amount of vent holes or an appropriately sized heat sink got in the way of Apple's Macbook Air design plans.

This is at least the case for the first generation Macbook Air in which the user community has documented overheating issues. These overheating issues can happen when doing intensive or even moderate tasks such as playing back video or surfing flash enabled sites.

At Go Go we are lucky enough to have access to 3 first generation Macbook Airs. Each of which was bought at separate times and so are not off the same assembly line. However, two of these are configured with 1.8Ghz CPUs and one is a 1.6Ghz. All have the SSD option.

Each one, when pushed with moderately intensive tasks or exposed to less than absolutely stellar environmental factors (rooms temperatures above 79 degrees), will exhibit heat issues that seem to induce the dreaded "kernel_task" process spike (kernel_task CPU usage can reach a steady rate of 150% from the Activity Monitor).

In one test, we had the 1.6Ghz Macbook Air in a room setting of 75 degrees on a nice flat desk surface area clear of any obstructions (so as to not block the vents) and connected to an Apple Cinema Display. We went to Apple's Movie Trailer site and decided to try to run a 1080p trailer. Using the Activity Monitor we set our timers to see how long it would take for the "kernel_task" process to spike in CPU usage.

Two minutes. Two minutes is all it took in playing an H.264 trailer from Apple's own site to bring the Macbook Air literally to its knees.

We also took the time to run temperature benchmarks and noticed that the CPU and Heat Sink temperature was almost directly correlated to the kernel_task process spike. When running normally the CPU and Heat Sink temperature were 134 and 125 Fahrenheit respectively but when running things such as video the CPU and Heat Sink reached levels of 147 and 134 Fahrenheit. Each time the kernel_process would spike in CPU usage when temperatures reached these levels. Even after quitting the video playback it would take sometime for the kernel_task to come down in usage levels until temperatures were back at nominal levels.

It's painfully obviously that Apple's cooling system for the Macbook Air is inadequate.

This is probably related to the almost useless thin heat sink employed in these Macbook Airs and the lack of adequate amount of vent ports to circulate air.

I should note that prior to the "kernel_task" issue was the Core Shutdown issue. Essentially, when Macbook Airs first shipped if the CPU would overheat the Macbook Air would shutdown one of the CPU cores as a safety measure. Obviously, customers complained and so Apple released a "fix" for this in the form of a firmware update.

Except that Apple didn't actually fix the overheat issue but instead stopped the CPU core from shutting down and implemented another type of fix to seemingly achieved the same results while keeping both Cores alive. Confused? That was Apple's point unfortunately in this scenario.

We will be contacting our sources at Apple to investigate the issue as standard support channels do not even acknowledge that an issue exist even though the first generation Macbook Airs have been out for a year and a half.

Our hope is to at least understand the role of the kernel_task process and see whether Apple is internally aware of the problem but publicly denying it.

Go Go


  1. I found this blog after googling around for a while. This is a great summary of the problem. It's been a year and I'm still having the issue...I doubt it will ever be fixed.

  2. Thanks for this article. Any new info on this? I'm having this problem a lot with my Mac Air.

  3. awesome, I want to have it, the work of steve jobs is always amazing