Snow 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.
and change it to
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.
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.