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Possible Duplicate:
Does a motherboard have to support 64-bit or is it just the CPU?

  1. For computer, being 32/64bit is a property of CPU, motherboard, or both?

  2. How do I recognize that "computer" is 32 or 64 bit? I only recongize it by looking if the Windows provided with it are 32 or 64 bit... but that's not ideal.

Community
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Tomas
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2 Answers2

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CPU determines this. However, you can install a 32bit OS on a 64bit processor

Dave M
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    And NOT vice versa. If you're running a 64-bit OS, you have to be on a 64-bit capable processor. – Shinrai Feb 15 '12 at 20:53
  • Thanks Dave. What do you mean by *"CPU determines this"*? Do you mean that motherboard doesn't have property of being 32/64 bit? Contrary to what I'd expect (the bus is on the MB also, isn't it?) – Tomas Feb 15 '12 at 20:58
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    The CPU, not the bus does the code interpreting. – edusysadmin Feb 15 '12 at 21:05
  • "Do you mean that motherboard doesn't have property of being 32/64 bit?" - Yes, just CPU. – Richard Holloway Feb 15 '12 at 22:06
  • @RichardHolloway, I thought that the 4MB RAM limitation is because some address limitations, which are present on the bus.... aren't they? – Tomas Feb 15 '12 at 22:46
  • Ah the 3GB problem! Have a look at http://en.wikipedia.org/wiki/3_GB_barrier and the section "Chipset and other motherboard issues" – Richard Holloway Feb 15 '12 at 22:53
  • @RichardHolloway, no no, please don't focus on RAM, I'm just asking: are you sure there is no bottleneck in the motherboard, that would disable the 64-bit CPU functionality? – Tomas Feb 15 '12 at 23:11
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It's a property of both the motherboard and the CPU collectively. A processor can be either 32-bit or have 64-bit extensions, but it needs a compatible motherboard to plug into. A motherboard could support 64-bit processors, but you could also plug a 32-bit one into it if you didn't need/want/afford 64-bit capability.

For question #2, there are several ways to determine whether the processor is operating in 32-bit or 64-bit mode. As others have commented though, this has been answered elsewhere.

Bigbio2002
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  • thanks, so can we say that I can't plug 64-bit CPU into 32-bit only motherboard? – Tomas Feb 15 '12 at 22:50
  • That's correct. The 32-bit motherboard would likely have been from an older product line, so it wouldn't support newer CPU families that are 64-bit capable. I suppose it's possible for a company to deliberately segment the market by selling 32-bit-only motherboards for cheaper, but pretty much all modern motherboards and processors are 64-bit capable. – Bigbio2002 Feb 15 '12 at 22:58
  • Thanks. Well, now I have 2 answers that seem to state completely the opposite, so I'm not really sure which one is correct. – Tomas Feb 16 '12 at 14:01