32 bit/64 bit OS? [closed]

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Closed 11 years ago.

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What are the differences between 32- and 64-bit operating systems?

And specifically, can 64-bit operating systems run on a 32-bit processor, and why, why not?

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• 32-bit OS uses 32-bit addressing (the address space is 4 Gbyte), 64-bit OS uses 64-bit addressing (the address space is 4G*4G, it's plenty).
• 64-bit OS requires 64-bit processor (processor, which use 64-bit addressing).
• 32-bit OS requires 32-bit processor, or 64-bit processor with backward compatibility mode (most of processors have).
• Programs written for 32-bit OS can run on 64-bit OS if the 64-bit OS has compatibility mode (usually has). Of course, I mean the same OS versions.
• The "how many bit" has different meaning in case of the processors: it means the data bus width (not 100% accepted term). Also, there are processors which are x bits, but they operate as x*2 bit, say, MC68000 is a 16-bit processor, because it has only 16-bit bus, but it use 32-bit addressing (altough it can only reach 24M), but it has 32-bit registers, so it's "logically" 32-bit. The smallest family member, MC68008, is 8-bit processor (same instruction set as MC68000, but only 8-bit data bus), only MC68020 (and above) are "true" 32-bit processors, because they have 32-bit data bus. That's why the MC68000 is mentioned as a 16/32 bit processor: it's a 16-bit processor with 32-bit programming architecture.
• Some 64-bit operating systems can provide separate 4 Gbyte address space for each 32-bit process, so it's worth to use 64-bit version of it.
• Some 64-bit operating systems can't use 32-bit drivers, so if you don't need 4G+ memory, or you don't have to use native 64-bit computing anyway, it's - yet - better to use 32-bit operating systems.
• 64-bit programs (programs which utilizes the processor's 64-bit instruction set) may run faster than 32-bit versions (depends on processing type they do), and may eat a little more space (because of double-size memory pointers).
• The main reason of choosing 64-bit is breaking the 4G memory limit per process: servers, video/image processing etc. Everyday office work requires no 64-bit processing (yet).

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Nopes!! Size of the instruction is the deal breaker!

You may have observed that Windows 7 has different packages for 32 and 64 bit platforms!

Shash

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Yes! for 32 bit OS. Each instruction only have 32 bits.