In order to switch the kernel boot mode in Mac OS X permanently you will be need to perform this at the command line. In order to determine the current kernal boot architecture setting run the following: systemsetup -getkernelbootarchitecturesetting In order to set the kernel boot architecture run the following:  sudo systemsetup -setkernelbootarchitecture i386 | x86_64 | default  For example, … More Switching Mac OS X kernel boot architecture