Snow Leopard loads 32-bit kernel by default. – MacNN Forums

Oh boy. Before the panic starts, let’s set a few things straight:

• you do NOT need a 64 bit kernel to run 64 bit apps; 32 bit SL WILL run 64 bit apps; SL is 64 bit compatible regardless of which kernel version you boot

• SL even if booted with the 32 bit kernel will still be able to run 64 bit apps and address more than 4GB of RAM

• the reason you’d need the 64 bit kernel is if the kernel needed to address more than 32 GB of RAM (hence it’s default on the Xserve) or you have a 64 bit only kext (developers)

• 64 bit kernels do not make your computer magically faster; unless you need more than 32 GB of RAM (IOW only Xserves anyway) you do not need it for addressing reasons either

• the reason Apple doesn’t force everybody to run a 64 bit kernel is because most people will have a third-party 32 bit device driver than isn’t compatible; if forced to run a 64 bit kernel people could throw those devices away

• by making 32 bit default on consumer systems and giving pros and developers the 64 bit kernel option Apple is retaining max compatibility AND max flexibility

• 64 bit is mainly a developer option; they can use it to test their new 64 bit drivers/kexts to make sure they work with the 64 bit kernel

• should you be a pro that actually needs a 64 bit kernel and is willing to sacrifice driver compatibility now, you are free to boot SL with the 64 bit kernel; there is even a defaults write command to write it to plist so you don’t need the key combo for every restart

If you now feel like panicking or ranting:
1) Take a deep breath
2) Read all of the above
3) Take another deep breath
4) Think (may be combined with step 3)
5) Repeat step 4 to be on the safe side
6) Read all of the above again
7) Do not panic or rant

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