32-bit vs 64-bit Mac & Snow Leopard

(Note: This is all based on Developper release 10A432 and is yet to be confirmed in the final release.)

If you’re upgrading your MAC OS to Snow Leopard (only $35 CAD) you should be looking to ensure you’re running the 64-bit version (although Apple claim users won’t notice the difference — and furthermore it would appear that Snow Leopard runs 64-bit applications regardless of how it booted).

Your first step is to determine if your processor is 64-bit capable or not.  You must have the 64-bit EFI. Here’s the chart from Apple:

Intel Core Solo 32 bit
Intel Core Duo 32 bit
Intel Core 2 Duo 64 bit
Intel Quad-Core Xeon 64 bit

Once you’ve determined if you’re 64-bit capable, you apparently need to hold down the 6 and the 4 simultaneously on a standard Mac at boot up to force the installation into 64-bit mode, otherwise your Snow Leopard will install in 32-bit mode by default.  Also see the com.apple.Boot.plist file for permanent changes.

I’ve searched support on Apple and only confirmed this in Snow Leopard Server.


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