Snow Leopard booting into 64-bit mode

[SpearMan]

By default, Snow Leopard boots into a 32-bit kernel. This tip is especially for curious people who want to try and feel comfortable enough with the terminal to perform the manipulations described.

Here are the advantages and disadvantages of the 64-bit kernel mode :

Advantage
A slight improvement in performance (not visible to a normal user)
Support more than 32GB of RAM (again little interest for a normal user)

Disadvantages
Incompatibilities with some software (VMWare Fusion, VPN software ...) and hardware drivers

Are you interested anyway? Then go on

• Having a 64-bit EFI.
• Having a graphics card other than the Intel Graphics Media Accelerator (GMA 950 or GMA X3100) with no 64-bit drivers.

To check:

Open Terminal (/ Applications / Utilities / Terminal)

Type:

ioreg-l-p IODeviceTree | grep firmware-abi

Result is displayed:

| | "Firmware-abi" = < "EFI64">

For the graphics card, see Hardware > Graphics / Displays in the application System Profiler (/ Applications / Utilities). If GMA somewhere that's not good.

If these two prerequisites are verified, well, you can continue.

What to do in all cases:

The traditional method is to add "arch = x86_64" in / Library / Preferences / SystemConfiguration / com.apple.Boot.plist

To do so we must open this file with root privileges:
Open Terminal

Type:

sudo / Applications / TextEdit.app / Contents / MacOS / TextEdit / Library / Preferences / SystemConfiguration / com.apple.Boot.plist

Replace:

<key> Kernel Flags </ key>
<string> </ string>

By:

<key> Kernel Flags </ key>
<string> arch = x86_64 </ string>

Save and quit TextEdit


But this is not enough on all machines, not including the MacBook and Mac Mini.

Case of machines not supported although a 64-bit EFI

If you have a machine that is not listed below (see Hardware tool System Information ( in / Applications / Utilities): check image Tool

Then continue with the following:

Download this file: boot64.efi see at end

Open Terminal and go to the download directory by typing:

cd ~ / Downloads

Type the following command:

./boot64.efi sudo cp / 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

done Restart your machine and you should be under 64-bit kernel.

[SpearMan]

In case of problems

To return to 32-bit operation requires: Start the installation DVD of Mac OS X

NOTE: If you can still start but you just have problems with 64-bit mode, then you can type the following command when starting normally. In this case, delete "/ Volumes / <Name of your hard disk >" at the beginning of commands, cons, keep the "/" initial path.

Once the selected language, go to the menu Utility and select Terminal

Edit com.apple.Boot.plist remove the argument arch = x86_64 to do so as early in the tutorial, you need to type in Terminal:

sudo / Volumes / <Nom_De_Votre_Disque_Dur> / Applications / TextEdit.app / Contents / MacOS / TextEdit / Volumes / <Name of your hard disk> / Library / Preferences / SystemConfiguration / com.apple.Boot.plist

Replace <Name of your hard disk> by the name of the volume containing your installation of Mac OS X. For example, if your volume is called Macintosh HD, must be replaced by <Name of your hard disk> Macintosh \ HD.

Note the "\". Indeed, in the terminal when you type a file path that contains spaces, it must precede the space with a backslash (ie "becomes" \ ").

And replace:

<key> Kernel Flags </ key>
<string> arch = x86_64 </ string>

By:

<key> Kernel Flags </ key>
<string> </ string>

Save and quit TextEdit

In case you also use the file boot64.efi, type and more the following command:

sudo bless - folder / System / Library / CoreServices / - file / System / Library / CoreServices / boot.efi

which will effectively restore the EFI boot file by default.

Restart your Mac normally.

[zongjielee]

thx, i have followed ur method and successfully set my macbook start in a 64 Bit mode.
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