To check which EFI version you have, type this into Terminal:
| ioreg -l -p IODeviceTree | grep firmware-abi |
And you will see either “EFI32″ or “EFI64″ returned to you.
If you have “EFI32″ returned, you cannot enable 64-bit Kernel and Extensions, but you are still able to run 64-bit Applications.
Now, you can either continue to hold “6″ and “4″ everytime you want to boot, or you can do the following:
Terminal and editing the following file:
sudo pico /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
In here, you will need to add the following kernel flag
arch=x86_64
Which should leave you with a file that looks like the following:
How to tell if you’ve successfully loaded the 64-bit kernel in Snow Leopard:
Launch System Profiler (Applications > Utilities > System Profiler or About This Mac > More Info…)
Click on the “Software” heading in the left pane
Check the “64-bit Kernel and Extensions” line for a Yes or a No.
This is what it looks like in 32-bit:
This is what it looks like when the 64-bit kernel and extensions are loaded:
