You mean it wasn’t 64-Bit in the first place? But I thought the big thing with Snow Leopard was that the OS ran in 64-Bit awesomeness? Well odds are your still running at 32-Bit. To check your own system head over to System Profiler and select “Software” from the menu. Second to last line will show you whether your running 32 or 64 bit. The quick and easy way to enable the 64-Bit Kernel and extensions is by restarting your Mac and holding “6” and “4” while its starting up. I noticed an immediate difference in performance after I started booting in 64-Bit!
Why didn’t Apple load 64-Bit by default?
Basically, it was to be fair to the older 32-Bit EFI boards found on older Macs which simply won’t run the full 64-Bit Kernel and extensions. Want to know if your Mac will support 64-Bit Snow Leopard? Check this out.
Note: Another reason Apple did not have Snow Leopard boot in 64-Bit mode by default is because some 3rd party drivers may not be compatible.