Amit Singh recently made a post about patching boot.efi for 64-bit support on macbooks(with 64-bit efi).
Here is simplified version of his post:
To run 64-bit kernel on any mac with 64-bit efi you need patched boot.efi file
You can find file named boot64.efi here
It enables 64-bit kernel support for some macmini/macbook/imac/macbookair models, which has 64-bit efi bootrom.
Download file to desktop, open terminal.app and run these commands
sudo cp boot64.efi /System/Library/CoreServices/
sudo chown root:wheel boot64.efi
sudo chflags uchg boot64.efi
sudo bless −−folder /System/Library/CoreServices/ \
Commands starting with sudo will ask you for your password.
Next step – add arch=x86_64 to file /Library/Preferences/SystemConfiguration/com.apple.Boot.plist to Kernels Flags section
Now reboot, your mac should boot 64-bit kernel, but some models missing 64-bit intel video drivers, for example macbook4,1 with gmax3100, so only internal display will work, without qe/ci/opengl.
if something goes wrong, boot leopard/snowleopard dvd (or another installed osx system) and run this command in terminal
sudo bless –folder /Volumes/YOUVOLUMENAME/System/Library/CoreServices \
p.s. if you have 32-bit efi, this commands will make no effect for you at all.