OS X 10.8 Mountain Lion is on its way, and we’re all looking forward to all the new features and tweaks that this latest version offers. Unfortunately, not every Mac user is going to be able to ugrade to Mountain Lion, though. While Macs generally have a long “active support” life, every iteration of OS X leaves a generation or two behind and Mountain Lion is no exception.
The big thing this time around is 64-bit compatibility. Your computer needs to not only have a 64-bit capable processor, but also 64-bit capable EFI boot firmware. Some Macs, like the 2006 and 2007 Mac Pros, have 64-bit processors, but their EFI firmware is only 32-bit capable, so they won’t be able to run Mountain Lion.