Why is it that 32-bit drivers cannot be used under 64-bit Windows (and I'll assume other 64-bit OSes?), while most 32-bit programs can run under a 64-bit CPU? I don't have a 64-bit OS or CPU, but someone asked me this question and I figured you guys would know the answer.

Anyone have a clue?

32bit programs cannot access the full 64bit system. There would need to be an extensive amount of mode switching just to get the driver to interact with a 64bit OS. The complexity would be very high and thus the potential for bugs would be correspondingly high.

Mac OS X 10.5 Leopard supports 32-bit drivers although Leopard is 64-bit OS.

It must have a cute thunking layer then? Or perhaps a lot of drivers run as usermode services?

That's interesting.

The closest thing Windows has is UMDF - user-mode driver framework.

Haha, it looks like Leopard has a 32-bit kernel even though its advertised as a 64-bit OS. What a fail.

http://forums.macrumors.com/showthread.php?t=383492

What is even more fail is some Mac zealot is flaming WOW64.

Doh, I remember hearing about that a while ago, but had forgotten about it.

Fail