I have an iMac running OS X 10.6.8. The processor is a 2.8 GHz Intel Core i7 and the machine has 4 GB of RAM. How can I boot the computer in 64-bit mode (instead of 32-bit mode) so that I can upgrade to OS X 10.9 and run Final Cut Pro 10.3?
To start up with a special kernel check this from Apple: Starting up with the 32-bit or 64-bit kernel in 10.6 and later:
Startup key combination (for current startup only)
If your Mac uses the 32-bit kernel by default, but supports the 64-bit kernel, you can start up using the 64-bit kernel by holding the 6 and 4 keys during startup.
If your Mac uses the 64-bit kernel by default, you can start up with the 32-bit kernel by holding the 3 and 2 keys during startup.
Your Mac will revert to the default kernel the next time you reboot it.
On-disk setting (persistent)
To select the 64-bit kernel for the current startup disk, use the following command in Terminal:
sudo systemsetup -setkernelbootarchitecture x86_64
To select the 32-bit kernel for the current startup disk, use the following command in Terminal:
sudo systemsetup -setkernelbootarchitecture i386
Note: This setting is stored in the
/Library/Preferences/SystemConfiguration/com.apple.Boot.plistfile and will take effect every time you start up from this disk. If you start up from a different disk, the setting on that disk, or the hardware default, will take effect.
To determine your currently running kernel open
Terminal.app and enter:
Running with the 64-bit kernel, the output will end with
RELEASE_X86_64 x86_64. Running with the 32-bit kernel, the output will end with
In your case you just have to update to Mavericks (Mac OS X 10.9). Mavericks doesn't contain a 32-bit kernel anymore and since your i7-processor is 64-bit, everything just works right out of the box without key strokes or modifying