[Tloewald]

Apple's "marvel of engineering" actually does. You can launch an app in 32-bit mode (while running in 64-bit mode) should you require interoperability with 32-bit components. All actually pretty neat. And given that most of an app isn't executable binaries (and hasnt been since forever) the size of executables isn't a big deal.

(A few years ago I had to run Safari in 32-bit mode to test unity web apps for the brief period where unity didn't offer a 64-bit plugin.)

[kevingadd]

You're saying that you can load a 32-bit device driver into a 64-bit OS X kernel? I think you're wrong.

[Tloewald]

You're right, although you can run 64-bit apps on the 32-bit kernel with 32-bit drivers.