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Snow Leopard 10.6 and 64-Bit What you Need to Know


SnowLeopardSnow Leopard is just around the corner, Recently Apple seeded build 10A432 [Rumored GM] to developers. Snow Leopard is known for it’s full 64 Bit implementation in Mac OS X. There are still lots of shadows about 64 Bit and Snow Leopard, We’ll try to make is easy so you can understand more about 64 Bit support in new Snowy Kitty. Snow Leopard supports enabling its new 64-bit kernel on certain machines, including the Xserve, Mac Pro, and MacBook Pro. Snow Leopard does not support PowerPC-based Macs (e.g., Power Macs, PowerBooks, iBooks, iMacs (G3-G5), all eMacs, and the G4 Mac Mini) at all. 10.6 System boots by default to 32-bit kernel on all Macs, except Xserve. But that doesn’t means you can’t boot with 64 Bit kernel, by holding down the ‘6’ and ‘4’ keys during boot, you can to boot into full 64bit mode but only if, your Mac has 64-bit EFI.

  • How to check Whether your Mac has the 32-bit EFI or 64-bit EFI : When you are reading this i m sure you understand that you can boot into full 64bit mode if your Mac has 64-bit EFI. Also note that Apple disabled 64-bit kernel support for any Macbooks, even  with 64-bit EFI. So if you have an older Mac Pro, iMac and you wants to check Whether your Mac has the 32-bit EFI or 64-bit EFI just enter the following command in Terminal.

ioreg -l -p IODeviceTree | grep firmware-abi

And you’ll get the answer either “EFI32″ or “EFI64.”

  • How to boot 64-bit Kernel by default at every boot : Though you have a EFI64 and 64-bit compatible Mac your install will boot into 32-bit  kernel by default. Thanx to Netkas for highlighting a trick to change default boot kernel. All you have to do is edit a string file in com.apple.Boot.plist To edit boot.plist navigate to /Library/Preferences/SystemConfiguration/com.apple.Boot.plist and open the boot.plist with text editor and find the following string.

<key>Kernel Flags</key>

and change it to

<key>Kernel Flags</key>

That’s it, now your installation will boot in to 64-bit kernel mode every time. So no more holding down the ‘6’ and ‘4’ keys during boot. Just in case if you need to boot the 32-bit kernel just hold down the ‘3’ and ‘2’ keys during boot.

Snow Leopard 10.6

Disclaimer : Apple could chose to change the limitations above via an EFI update at any time. To keep your self updated with latest ramblings of Snow Leopard and Apple subscribe our free daily E-Mail news letter or follow us on Twitter.


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Comments ( 19 )

Have Something To Say ?

  1. ptesone October 19, 2010 Reply

    will -force64 be the same as arch=x86_64 ?

  2. masroor March 21, 2010 Reply

    hi Author,
    I did tried your trick of editing .plist file in com.boot.apple.plist
    But still i get the same error message , “The Mac os x 10.6 cannot be installed on this Computer”.
    As you have mentioned in typing the terminal i got this message.
    “| | “firmware-abi” = ”

    But still inVane.
    Please help me i will be very thankfull to you and very much greatfull to you .

    Masroor Ahmed
    Please mail me ..

  3. Velocityg4 February 23, 2010 Reply

    The author did not mention this but for people that have never edited any of the system files the following would be useful to know.

    Option 1:
    1. Enable root (http://snowleopardtips.net/tips/enable-root-account-in-snow-leopard.html)
    2. Make the edit
    3. reboot

    Option 2 (Safer for novices):
    1. copy the file to the desktop
    2. edit the file
    3. copy it back to the location
    4. open Terminal
    5. In Terminal you will need to input the following entries* (you can copy and paste the commands)

    sudo chown -R root:wheel /Library/Preferences/SystemConfiguration/com.apple.boot.plist

    sudo chmod -R 755 /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

    6. For good measure open Disk Utility and repair permissions.
    7. reboot.

    The reason for either of these procedures is that the file being edited is a System file. By enabling and logging in a root you are the System and have privileges to edit system files. With option 2 since you are not the System, you must edit the file in a non System folder. After placing the file back in a System folder you have to run the above Terminal commands to change the ownership of the file back to the System. Otherwise the System will ignore the file it has no privileges to and create a new default com.apple.boot.plist file.

    *Note: As I recall, to input these entries your Administrator account must have a password. Terminal will not accept a blank password. You must also be logged on as an administrator.

  4. alex February 17, 2010 Reply

    i have tried the plist edit and it comes up The document “com.apple.Boot.plist” could not be saved. plz help i dont know what this means

  5. Steve October 16, 2009 Reply

    I’ve looked all over, and can’t find /SystemConfiguration or com.apple.Boot.Plist anywhere. Any alternative means of doing this?

  6. Serge October 15, 2009 Reply

    I have MacBook Pro 15″ Model: MacBookPro3.1 with Core 2 Duo 2.2GHz freshly installed MAC OS X 10.6 and updated to 10.6.1 plist has been changed to boot in x64 mode. But it wasn’t booting in x64
    uname -a return following: Darwin Kernel Version 10.0.0: Fri Jul 31 22:47:34 PDT 2009; root:xnu-1456.1.25~1/RELEASE_I386

    Other MacBookPro with Model:MacBookPro4.1 working in x64 mode perfectly.

    How I can get x64 mode working on old machine?

  7. Gus September 6, 2009 Reply

    Mine shows EFI64 also, but still won’t boot into 64 bit Kernels.

  8. Dan September 4, 2009 Reply

    I cannot seem to find /Library/Preferences/SystemConfiguration/com.apple.Boot.plist on my computer anywhere…I did already install snow leopard before making it 64 bit…does that have to do with it at all?

  9. Tony September 3, 2009 Reply

    17″ Macbook Pro.

    Will not boot into 64bit, even if I edit the plist.

    64bit Windows 7 works perfectly (ish, given how flaky the 64bit bootcamp stuff is) so it’s perfectly capable.

  10. josh September 1, 2009 Reply

    MacBookPro 3,1.

    The machine reports “EFI64” but whatever I do, I can’t get it to boot into 64-bit mode. Tried “6” & “4”, tried changing the plist. No go. Any ideas?

  11. Andre August 30, 2009 Reply

    As for testing how this works,

    I have gottten it to work flawlesly on my mac pro, and not all desired effects on my macbook air, and both are EFI 64, since both have been bought new this year

  12. Andre August 30, 2009 Reply


    In response to your question on
    ” Also my G5 just serendipitously died. So I will be buying soon. Any speculation as to when a xeon/core i7 iMac may be coming? If it’s sept-ish I can wait, but can’t imagine being without a pc till Feb or whenever. ”

    The xeon/core i7 came out about half a year ago, and is avaialble already, but be aware prices start for a singple xeon/core i7, and for some $$ you can get a dual xeon/core i7 prices start at 2400 euro for single, and around 3000 euro dual, at least around here in Europe

  13. lololol August 29, 2009 Reply


  14. Bernie August 24, 2009 Reply

    The automatic 64-bit boot trick works for my 15″ Unibody MBP (June 2009). What I did was I downloaded the application Pseudo, which allows you to run applications as root. Using “sudo -a Textedit” did not seem to achieve the same effect. Anyhow, drop com.apple.Boot.plist into the window that pseudo creates, and it should open it in BBEdit or Textedit as a file that you can save changes to.

  15. Richard August 24, 2009 Reply

    What’s the advantage/disadvantage of booting in 64-bit vs. 32-bit? Is this something the average user should do? Will there performce differences? Will my Mac not take full advantage of “snowy kitty” if I don’t d this?

    Also my G5 just serendipitously died. So I will be buying soon. Any speculation as to when a xeon/core i7 iMac may be coming? If it’s sept-ish I can wait, but can’t imagine being without a pc till Feb or whenever.

    Thanks for any response to either issue!

    • Vinay August 24, 2009 Reply

      @ Richard There are lots of confusions over 32 bit kernel and 64 bit kernel. First of all 32 bit kernel is capable of running 64 bit apps and it supports RAM up to 32 GB, The basic difference between 32 bit kernel and 64 bit kernel is 64 bit supports more than 32 GB RAM. Thats why Apple restricted consumer Macs to boot default in 32 bit kernel and Xserve to boot default in 64 bit.

  16. Justin Esgar August 20, 2009 Reply

    Are we sure this works? I just tried it on my MacBook Air (yes I’m an apple developer), and even after rebooting I still get “no” for 64-bit Kernel and Extensions.

    • Vinay August 20, 2009 Reply

      @ Justin Esgar Thanx for showing interest to our article, According to MacFixit MacBook Air: Late 2008 and later are capable of running 64-bit kernel.

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