Do you think Microsoft should adopt the same 32/64 bit system that Apple has?

Can the 64-bit version of Windows boot into a 32-bit kernel? ("MinWin" I believe it's called for Win7).

That's something Snow Leopard can do, and if Windows 64-bit could boot a 32-bit kernel, then it would work on processors that do not support the X86_64 instruction set.

Then you only need one version of Windows, not two.

That's something I mentioned in my original post, that Snow Leopard can boot into either the 32-bit or 64-bit kernel.

First of all, MinWin has nothing to do with Windows 7. It's an internal Microsoft experiment dealing with creating a modular kernel. It's believed that a lot the the research on MinWin went into the Windows Embedded platform.

64bit Windows does not need to boot into a 32bit kernel. It can run 32bit software using the Windows-on-Windows (WoW) compatibility layer with the 64bit kernel in place.

In addition, most the resources and software that come as part of 64bit Windows are actually compiled in 64bit. Booting into a 32bit kernel would make it impossible to load these resources and applications (breaking Windows). Microsoft would have to have both a 32bit and a 64bit version of every system file in order to make swapping kernels possible. This would almost double the size of a 64bit install.

And what would all that gain you? ...nothing! People with 32bit processors experience no change at all, people with 64bit processors get a boot mode that makes the OS incapable of running 64bit applications, and both parties would have an OS install that's double the size. Absolutely pointless.

Microsoft skips this pointlessness by simply compiling the 32bit and 64bit versions separately. Both of these are compiled from the exact same code, meaning it really is a single version (just compiled for different CPU architectures). Even product keys are universal, one Windows Vista or Windows 7 product key will work with both the 32bit and 64bit installation media of its designated SKU.

Nope, Snow Leopard is both ;) All the base apps that come with the OS are 64-bit, but the OS has the ability to boot into both kernels.

There's a reason it's called a "fat" binary. Every additional architecture you add support for increases the file size.

Big waste of space when you only use one of those architectures.

Not entirely. a binary file for an app in Mac OS X is actually quite small in most cases because much of the code is held within pre-made system frameworks. Most object files with two or more archs in them are about 1-3MB, and with LLVM they've gotten even smaller now.

The major cause for large app sizes is the resources like localization files. Just in iTunes, the localization resources take up 140MB.

@Leapo if you look at the filesize of Snow Leopard, compared to the filesize of Windows 7, you'll notice what you said is inaccurate.

@Granit I realize that, but I'm mostly talking about the Kernel, which is why I specifically mentioned Snow Leopard.

@ Eric: Think about what you just said for one second. Just because Snow Leopard is smaller overall than Windows 7 doesn't mean that these fat binaries aren't larger than they would have been without all the alternate architecture support rolled in.

Windows has a lot more to support; legacy application compatibility, multiple graphics libraries, far more drivers, the list goes on. This contributes to its final size. It has so much extra support, and so many extra features, that even with normal binaries it's larger than Snow Leopard.

A lot of OSX's bulk, on the other hand, appears to be these fat binaries. Apple themselves claims massive space savings simply from the removal of PowerPC support in Snow Leopard.

the fat binaries themselves take up little extra space, and part of the code such as the dynamic runtiime data is shared between archs. The major issue is localization data... having 20-30 interface sets of different languages you'll never use. Adding another arch does increase the fat binary, normally by about 1/3 the original size... but the binaries tend to take up about 1-5% of the total app bundle size itself.

I've seen some apps weighing in at 200MB and they have a 1-2MB binary