Determining whether your Mac has 32-bit or 64-bit firmware

As documented yesterday in my Snow Leopard Special Report on performance, booting the Snow Leopard 64-bit kernel is awesome news for performance, the best ROI (return on investment) I’ve ever seen for an OS upgrade.

The bad news is the Macs a few years old have 32-bit firmware (including original Mac Pro models), which makes them incapable of booting the 64-bit kernel, and you thus forgo all the speed advantages of a 64-bit kernel.

Here’s how to determine if your Mac has 32-bit or 64-bit firmware.