How to boot 64 bit

http://support.apple.com/kb/HT3773

What version of OS X is it running?

Odds are unlike PCs it is already running 64 bit.

Allan

Just so you know, the Mac doesn't need to boot 64 bit in order to run 64 bit apps. The kernel will happily run 32 bit while still running 64 bit apps as 64 bit.

To check and see how your Mac's kernel is running, hold down the Option key and click on the Apple at the top left, then choose System Profiler. In the left column, click on Software. Look at the right under 64-bit Kernel and Extensions. If it says Yes, then you're already booting 64 bit. No, of course means the kernel is running 32 bit.

If it says No, and you'd prefer the Mac always boots 64 bit, do this:

Here's the configuration file approach for always booting into 64-bit. This is the best way to make your Mac always start up 64 bit as the only thing necessary is to alter one line of a configuration file. You can do that by opening the Terminal and entering the following line. You can also copy/paste it from here into the Terminal window. Note that it is a single line, though it shows as wrapping in this post.

sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.Boot 'Kernel Flags' 'arch=x86_64'

To return to 32 bit mode, you would repeat the command but enter an empty string, which would just be the single quotes (where arch=x86_64 is) with nothing in between.

sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.Boot 'Kernel Flags' ''

Be aware that if any device drivers you have (tablet, mouse, scanner, etc.) are 32 bit only, they won't load under a 64 bit startup, and therefore, won't work.

Allan Doyle2 wrote:

Just picked up a 3.2 8 core. How do i boot 64bit mode?

How do you know you are not already running in 64-bit mode?

Open the System Profiler (in Utilities) r launch it from More Info in the Apple menu, About this Mac. Click Software in the left pane. Does it say 64-bit Kernel and Extensions is Yes in the right pane?

Also, in terminal, copy/paste the following line into the terminal window:

uname -a

Hit reutrn. Does the output say "RELEASE_X86_64 x86_64" near the end of the output line?