One feature that Apple “bragged” about in their newest operating system, Snow Leopard, is its ability to run 64-bit apps, kernel and extensions. Well, by default, if the app can, it runs in 64-bit mode. On the other hand, Snow Leopard boots into 32-bit kernel and extensions by default on every Mac OS X computer, except for Xserve, Apple’s Mac OS X based server. Here are three ways to boot Mac OS X Snow Leopard into 64-bit kernel and extensions. Please note that not all Mac computers support 64-bit. Here is a list of Macs that currently can boot into 64-bit mode:

Method 1: Temporarily boot Snow Leopard into 64-bit mode. Once restarting again, it will boot into 32-bit mode

Step 1: Shut down or restart your Mac

Step 2: Once you hear the startup tone, hold down the “6″ and “4″ keys simultaneously. Keep holding them until you see the desktop or login window

Step 3: Check to make sure you booted properly into 64-bit mode: Apple Menu>About this Mac>More Info…>Left Sidebar>Software. If you booted properly, ”64-bit Kernel and Extensions” should say “Yes”

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Method 2: Force Snow Leopard to boot into 64-bit automatically

Step 1: Navigate to: /Library/Preferences/SystemConfiguration/com.apple.Boot.plist. Right click>Open With…>TextEdit (or any other text editor)

Step 2: Find the following text:

<key>Kernel Flags</key>

<string></string>

Step 3: Change it to:

<key>Kernel Flags</key>

<string>arch=x86_64</string>

Step 4: Restart your Mac

Step 5: Check to make sure you booted properly into 64-bit mode: Apple Menu>About this Mac>More Info…>Left Sidebar>Software. If you booted properly, ”64-bit Kernel and Extensions” should say “Yes”

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Method 3: Use an application to boot Snow Leopard into 64-bit mode

Step 1: Download and install this application, Startup Mode Selector: http://www.ahatfullofsky.comuv.com/English/Programs/SMS/SMS.html

Step 2: Follow the steps given in the application

Step 3: Restart your Mac

Step 4: Check to make sure you booted properly into 64-bit mode: Apple Menu>About this Mac>More Info…>Left Sidebar>Software. If you booted properly, ”64-bit Kernel and Extensions” should say “Yes”