Saludos How To: Enable 64-bit As Default In OS X Snow Leopard

The latest version of Apple's Mac OS X "Snow Leopard" will be released on August 28th, 2009. Those of us who will be upgrading, or are using build 10A432, which is the "Golden Master", may realize that by default, 64-bit kernel and extensions is not enabled.

If you are running Snow Leopard, or when you do run Snow Leopard, you will notice on all machines except for XServe machines, that 64-bit kernel and extensions will look like this in System Profiler:

System Version: Mac OS X 10.6.1 (10A432)
Kernel Version: Darwin 10.0.0
Boot Volume: Macbook HD
Boot Mode: Normal
Computer Name: xxxxx-xxxxxx
User Name: xxxxxx-xxxxxx
Secure Virtual Memory: Enabled
64-bit Kernel and Extensions: No
Time since boot: 1:37

As you can see, 64-bit Kernel and Extensions is currently saying No.

Also, you may know that you can enable 64-bit Kernel on some (capable) machines by holding the "6" and "4" keys at boot. This will only work on (capable) machines, and those machines must have a 64-bit EFI.

To check which EFI version you have, type this into Terminal

Copy paste Terminal

ioreg -l -p IODeviceTree | grep firmware-abi

And you will see either "EFI32" or "EFI64" returned to you.

If you have "EFI32" returned, you cannot enable 64-bit Kernel and Extensions, but you are still able to run 64-bit Applications.

Now, you can either continue to hold "6" and "4" everytime you want to boot, or you can do the following:

Navigate to the following location in Finder:
Copy paste Terminal

/Library/Preferences/SystemConfiguration/com.apple.Boot.plist

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


From there, find this bit of text: And add arch=x86_64 between the <string> tags, so that you have this:

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


Save the file, and reboot your machine. If you have a (capable) Mac, you will see "Yes" in System Profiler, instead of "No".

If you want to boot into 32-bit, just hold "3" and "2" at boot, or edit the file again, and remove that string.

Hopefully this helps some of us with a Mac and Snow Leopard.

Cheers!

Edit: I have realized, that in System Profiler, it may still display "No".

You can check if you are running 64-bit by default, by checking Activity Monitor, and next to each process, if it's enabled as 64-bit, it will say "Intel (64-bit)".

This would not be displayed if you were not running the 64-bit kernel, to my knowledge.

You can also view it in System Profiler by clicking "Extensions", which will display most, if not all, of them as 64-bit enabled.

System Version: Mac OS X 10.6.1 (10A432)
Kernel Version: Darwin 10.0.0
Boot Volume: Macbook HD
Boot Mode: Normal
Computer Name: xxxxx-xxxxxx
User Name: xxxxxx-xxxxxx
Secure Virtual Memory: Enabled
64-bit Kernel and Extensions: Yes
Time since boot: 1:39