Snow Leopard: going to a full 64-bit OS

"The apps will go 64 bit as time permits, I'm sure. Stay up to date and 64 bitness will gradually pervade your non-Apple (and Apple's -- many Apple apps are still 32 bit and will likely be for a while) applications.

Unless you can eliminate every last 32 bit process from your machine, there is no penalty to running 32 bit applications in that all of the 32 bit versions of the frameworks & dylibs will be loaded anyway."

You can use the built-in 64-bit Preview application to replace most of the functionality of Adobe Reader. There isn't a 64-bit version of iTunes, Dropbox, Flash Player or Evernote yet.

"Some applications are not available in 64 bit. Some applications won't be available in 64 bit. And some applications don't have to be available in 64 bit.

Snow Leopard, as did leopard, only supports 64 bit Darwin and Cocoa applications (ignoring Java). Carbon remains 32 bit. iTunes is a Carbon application and will remain 32 bit until Apple rewrite huge parts of it to port it to Cocoa.

Apparently all of the Cocoa applications (except Terminal.app?) that came with Snow Leopard are not 64 bit (if running on a 64 bit computer). But for some applications there is simply no benefit of running them as 64 bit code.

Incidentally, I found that the Snow Leopard kernel and many (or possibly all) of the Unix tools are universal binaries supporting x86 (32 bit Intel), x86_64 (64 bit Intel) and PPC (PowerPC)."