A few questions about 64 bit and Windows...

[Elysia]

Apps compiled as 64-bit apps won't run in x86 windows. However, you CAN still compile them as 32-bits. They'll run on both x86 and x64.

I really don't see much benefit of 64-bit, except for some more memory that you don't need right now. It's the future, yes, but it's not worth spending a lot of money on IMO. You can't upgrade to 64-bit, you'll have to reinstall Windows. But I can't speak for drivers.

About Vista. I think Vista is actually becoming usable. I've been using it for a while with little problems. No, it's not a great improvement over XP. A lot of it is overhyped. Better can be argued, though. I say it has better tools, nicer interface and features. However, it's more of a resource hog plus there's compatibility problems with some things. If I were asked, is it worth investing in - as in buying, the answer is NO. Is Vista usable - is it something I should get eventually? The answer would be yes, since future Windows are built on Vista's architecture (I'm thinking of Windows 7 here). It should be painless to upgrade from Vista to Windows 7, but not from XP.

That's my thoughts on the whole.

[matsp]

I really don't see much benefit of 64-bit, except for some more memory that you don't need right now. It's the future, yes, but it's not worth spending a lot of money on IMO. You can't upgrade to 64-bit, you'll have to reinstall Windows. But I can't speak for drivers.

Actually, many applications run faster in 64-bit than 32-bit - particularly if you have many function calls with quite a few parameters, as 64-bit having more registers pass the first 5 or 6 arguments in registers, whilst 32-bit can only use at the most 3 registers for passing arguments. More registers also help the code generation in the functions themselves, as it allows the compiler to keep more data in registers without having to load/store so much. Code on x86-64 is usually about 15% instructions less than the same code compiled for x86-32 (using the same compiler - obviously, different compilers will perform more or less well on a particular piece of code in general). 15% fewer instructions in itself gives a 15% speed improvement, but avoiding potentially lengthy memory operations often give more than that.

However, I have seen people indicate that applications would run twice as fast on 64-bit as they do on 32-bit. This is true for some special cases, but in most cases, those are the same that run 2/4x faster if implemented in MMX/3DNow and SSE respectively - and once that is done, there is little or no benefit from moving to 64-bit.

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Mats