How to stop your Macbook Pro 2011 from experiencing a Kernel Panic when tethered to an iPhone

So Apple unfortunately has quite a frustrating bug in on their 2011 Macbook Pros (and possibly other systems) whereby the machine will intermittently experience Kernel Panics when connecting to the internet via USB tethering using an iPhone. Reports are that this happens on multiple versions of both Snow Leopard and iOS, and that it’s very likely to happen on 2011 Macbook Pros, but can also happen on older machines. As both Henk (Firestar) and Paul (Artagra) have Macbook’s and iPhones, this was an issue for us! 

Image Courtesy Apple Inc

This is a definite problem that Apple needs to fix, but fortunately there are two possible solutions available while we wait for Steve Jobs to break out his magic coding ninjas: 

• Tether via Bluetooth. This problem does not happen while tethering over Bluetooth. However, please note that even if you remove the iPhone USB connection from connection manager, if the iPhone is still plugged in via USB (for charging) but tethered via Bluetooth, you will still have intermittent kernel panics. 
• Switch over to the 32bit Kernel. If you are running the 32bit kernel, this problem does not happen. 

According to Apple, there are two ways to change to the 32bit Kernel:

To change to the 32bit kernel for only one boot, hold down the 3 and 2 keys on your keyboard during boot. 

• To change permanently to the 32 bit kernel, enter the following command into terminal: 
  sudo systemsetup -setkernelbootarchitecture i386
   
• And to change back to the 64bit kernel, enter the following: 
  sudo systemsetup -setkernelbootarchitecture x86_64

“But won’t running the 32bit kernel make my Apple run like a 3 legged dog?” 

Well firstly, the 3 legged dogs I’ve seen are pretty quick. But in all seriousness, no. Apple made some very smart decisions during the development of 64 bit versions of OS X that allow 64 bit software to run even when you have the 32bit kernel, and that allow the 32bit Kernel to address more than 4gb of Memory. Quoting the always informative John Siracusa of Arstechnica: 

“Finally, this is worth repeating: please keep in mind that you do not need to run the 64-bit kernel in order to run 64-bit applications or install more than 4GB of RAM in your Mac. Applications run just fine in 64-bit mode on top of the 32-bit kernel, and even in earlier versions of Mac OS X it’s been possible to install and take advantage of much more than 4GB of RAM.”

If you are interested in the 32 to 64 bit transition on Macs, definitely go and read the Arstechnica review on Snow Leopard - they have a great section dedicated to the transition. It’s also interesting to note that the Mac Pro (Mid 2010) and Macbook Pro (Early 2011) are the first macs to boot by default into the 64bit kernel. 

Hope that helps some of our Macbook using readers!