32- or 64-bit Kernel Startup Mode Selector for Mac

MacOS X 10.6 Snow Leopard is 64-bit - or is it?. Well, actually MacOS X 10.6 Snow Leopard is both 32-bit and 64-bit, and what that means for you depends on both your hardware and your settings.

I put up an accompanying 0 website which should answer most of your questions at

What does this app do?

• it shows whether you have a 32-bit or a 64-bit processor
• it shows whether you have a 32-bit or a 64-bit EFI
• it shows whether the MacOS X Kernel is set to boot in 32-bit or in 64-bit mode
• it shows whether the MacOS X Kernel is running in 32-bit or in 64-bit mode
• it shows whether Apple officially supports booting a 64-bit kernel on your Mac
• it allows you to select whether you want to start the MacOS X Kernel in 32-bit or in 64-bit mode (the setting might be ignored on MacBooks, depending on how Apple implements the restriction)
• accompanying webpage explains what the whole commotion about 32-bit and 64-bit in MacOS X Snow Leopard is about