I'm customizing a new computer.

[downphoenix]

Originally Posted by Power666

Because when a 32 bit program as for a memory address from the operating system, it expects to get 32 bit back and not 64 bits.

There are even more fun things in the 32 bit to 64 bit transition too. The memory space is now flat in x86-64 where there were tons of old arcane tricks dating back to the x86's 8 bit roots under 32 bit mode. The 64 bit mode reduces a lot of headaches but for older programs that were programmed around these issues, it is a compatibility concern.

I was under the impression that at least Vista 64 Bit allows you to run 32 bit applications and the only real issue was whether the user had proper 64 bit drivers for hardware.

[Power666]

Originally Posted by downphoenix

I was under the impression that at least Vista 64 Bit allows you to run 32 bit applications and the only real issue was whether the user had proper 64 bit drivers for hardware.

It does but there are some applications that won't work in Vista 64 bit that will in Vista 32 bit. Hence the compatibility concern, not flat out incompatibility.

[E6600]

Apple got 1 version of Leopard capable of running both 32bit and 64bit applications, couldn't Microsoft just do the same?

[Power666]

One advantage Apple had is that their legacy software (ie everything OS 9 and below) ran inside a virtual machine. That allowed Apple to plan ahead for the 64 bit transition. In fact, OS X isn't entirely 64 bit but they started out the OS X to move towards that direction. The kernel was 64 bit back in OS X 10.3 and command line applications could be 64 bit under OS X 10.4 and all user space applications in OS X 10.5. There are bits that are still 32 bit under OS X 10.5 and in reality there isn't an overwhelming need to migrate those to a 64 bit environment. One of the little known things is that PowerPC chips actually work faster on 32 bit code than 64 bit code. With all other things being equal, 32 bit code should always be faster than 64 bit code. The catch with the x86 processors is that things are not equal with more registers and better memory handling in 64 bit mode. The other trick Apple employs is how they bundle several binaries together as one file. A modern OS X 10.5 application can include the 32 bit PowerPC, 32 bit x86, 64 bit PowerPC, and 64 bit x86 code all together. If Apple were to support another hardware architecture (which they are with the iPhone's ARM based CPU), it'd be a logical extension of what they're already doing.

As for MS, they could have put some forethought into 64 bit computing when they moved the Windows NT kernel to the average user with Windows XP. Had MS layed the ground work then, the transition would be much smoother. Breaking stuff between Windows 98 and Windows XP was expected for really old applications and it really wouldn't have made a difference at the time. What is interesting is that there was a 64 bit port of Windows 2000 to the Alpha architecture that was never released. MS actually had some sort of transition figured out back then but they never followed through (Windows 2000 for Alpha was never released but beta were given out to developers).

[E6600]

A modern OS X 10.5 application can include the 32 bit PowerPC, 32 bit x86, 64 bit PowerPC, and 64 bit x86 code all together.

Universal binaries is a smart move, just like Fat binaries before, makes it easier to just find an app and install it. Though some of them are Intel or PowerPC specific.

[InsightGoalie]

Originally Posted by Power666

It does but there are some applications that won't work in Vista 64 bit that will in Vista 32 bit. Hence the compatibility concern, not flat out incompatibility.

Yeah, but those applications are few and far between. The only issue I had with going to Vista x64 was that McAfee didn't work. I had to get the enterprise edition. Other than that it's been smooth sailing.