Amit Singh recently posted how to patch your macbook with the 64-bit kernel enabled, here i’ll try to explain why you’d want to do this and guide you thru the process of making this happen.
Technicals
First off this article assumes you have a Snow Leopard installed on your macbook, and that it’s one of the newer ones with the Intel Core 2 Duo processors. Core Duo’s only support 32-bit mode, Core 2 Duo’s have a 64-bit instruction-set and so are capable of running the 64-bit Kernel & 64-bit EFI; think of the EFI as your system bios done much better.
Why
Well the problem here is that when Snow Leopard came out, it heralded the age of a full 64-bit machine, efi, kernel, software, the works. However there was a problem, a lot of original intel mac hardware was only capable of 32-bit mode, so they had to make a decision, enable 64-bit mode and annoy particular users or leave it in-active and gradually ramp up the ones that could; thankfully they opted to allow all intel mac’s access and then ramp up support as things progress.
Now newer hardware should come with the 64-bit kernel enabled, giving you faster throughput, and as everythings going that way you’d probably want to be there.
Now with my macbook, an aluminium unibody 13" Intel Core 2 Duo 2.0ghz macbook, I couldn’t get the 64-bit kernel enabled, only the 64-bit EFI; however by patching the BOOT.EFI file managed to enable it.
How
To run the 64-bit kernel, you’ll need:
- Snow Leopard
- Intel Core 2 Duo Mac
- a 64-bit efi
- and a patched boot.efi file
The patched file enables 64-bit kernel support for some macmini / macbook / imac / macbook-air models, which have the 64-bit efi bootrom.
Download the file to your desktop, open Terminal and:
cd ~/Desktop
sudo cp boot64.efi /System/Library/CoreServices/
cd /System/Library/CoreServices/
sudo chown root:wheel boot64.efi
sudo chflags uchg boot64.efi
sudo bless −−folder /System/Library/CoreServices/ \
−−file /System/Library/CoreServices/boot64.efi
Commands starting with sudo will ask for your password.
Next,
nano /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
And add arch=x86_64 to the Kernels Flags section, e.g.
<key>Kernel Flags</key>
<string>arch=x86_64</string>
Now reboot, your mac should boot up with the 64-bit kernel, but some models missing 64-bit intel video drivers, for example macbook4,1 with gmax3100 may not.
If something does go wrong, boot with the Leopard / Snow Leopard DVD and run this command in terminal
sudo bless –folder /Volumes/YOUVOLUMENAME/System/Library/CoreServices \
–file /Volumes/YOUVOLUMENAME/System/Library/CoreServices/boot.efi
How do I Tell ?
Open up System Profiler, click Software and you should see:
64-bit Kernel and Extensions: Yes
Update – Problem with 10.6.1
Alas the recent OSX update 10.6.1 was sent out which looks to have made this whole process mute, even if you hard-wired the boot file. Obviously they didn’t want certain machines running 64-bit mode after all. Thankfully as long as you aren’t one of the lucky ones with more than 4GB RAM you won’t notice it, 32-bit and 64-bit apps should run peachy regardless.
Enjoy, it was fun while it lasted.
