Starting Mac Lion in 32bit/64 bit mode

After upgrading to Lion, thing that I realized is that my iMac is starting in 64 bit mode.

Here is a tip to start your Mac in  32 bit or 64 bit mode at the startup.

– if your mac uses 64 bit kernel by default, you can start up with the 32 bit kernel by holding the 3 and 2 keys during startup.

– similarly if your mac starts in 32 bit kernel by default and supports 64 bit kernel, you can start up with the 64 bit kernel mode by pressing the 6 and 4 keys during startup.

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

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

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