I was stunned the other day when I was looking through my system info on my Snow Leopard equipped Mac Book Pro to find it was running in 32bit modeβ¦. Turns out you have to manually configure it to run in 64bit every single time you boot up (as seen further below), or by holding down 6 and 4 on the keyboard at startup.
The permanent fix:
Edit the file:
/Library/Preferences/SystemConfiguration/com.apple.Boot.plist
Insert arch=x86_64 into the Kernel Flags field.
Kernel mach_kernel Kernel Flags arch=x86_64via Macintosh Performance Guide: Mac OS X 10.6 Snow Leopard: Booting the 64-bit Kernel.