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New MacBook Pros default boot in 64-bit mode

Seth Weintraub | Mar 20 2011 - 5:17 pm PT

Here’s an interesting little tidbit we didn’t notice until just now: Apple boots those new MacBook Pros into 64-bit Snow Leopard rather than 32-bit, like every other Mac out there save the Mac Pro (which the MacBook Pro certainly competes with and juice up to 16GB of RAM). We’re sure some people noticed it before but we hadn’t seen it elsewhere.

Also of interest, the new MacBook Pros have 6Gb SATA III which was benchmarked pretty spectacularly by BareFeats. Unfortunately, the optical drive only has 4Gb SATA II for you SSD-in-optical-bay modders.

To switch between 64 and 32-bit modes on your 64-bit supported Mac, you can use either of these methods:

Method 1: Startup key combination (for current startup only)

If your Mac uses the 32-bit kernel by default, but supports the 64-bit kernel, you can start up using the 64-bit kernel by holding the 6 and 4 keys during startup.
If your Mac uses the 64-bit kernel by default, you can start up with the 32-bit kernel by holding the 3 and 2 keys during startup.

Your Mac will revert to the default kernel the next time you reboot it.

Method 2: On-disk setting (persistent)

To select the 64-bit kernel for the current startup disk, use the following command in Terminal:

sudo systemsetup -setkernelbootarchitecture x86_64

To select the 32-bit kernel for the current startup disk, use the following command in Terminal:

sudo systemsetup -setkernelbootarchitecture i386

Note: This setting is stored in the /Library/Preferences/SystemConfiguration/com.apple.Boot.plist file and will take effect every time you start up from this disk. If you start up from a different disk, the setting on that disk, or the hardware default, will take effect.

Thanks Kyle!