What is meant by "64-bit support" for processors?

What is meant in Newegg's descriptions of processors by "64-bit support"? I know that 32-bit processors can handle 64-bit (or even 128-bit variables). Does this refer to memory allocation? That is, is it able to reference memory addresses beyond 4 GB when a processor that has no 64-bit support can't? Or, does it refer to it being faster with 64-bit variables? Windows calculator uses a 128-bit floating point variable since Windows 98 at the earliest known (back when 16-bit processors were probably still in use).
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  1. I believe it means the integer units have 64-bit capability in addition to the 64-bit memory address capability you mentioned. Floating point units are a completely separate entity.
  2. Basically, 64-bit capable refers to 64-bit memory address capability.
  3. 64 bit support refers to multiple things, primarily that it uses a 64 bit address space or close enough so that it can run a 64 bit OS, secondly it refers to the architecture as 64 bit CPUs have slightly different architecture with more registers than 32 bit only CPUs have.

    How large the int and FP units are is a different thing and not related to being 64 bit support.
  4. 64 and 32 bits are width of processing channel (capability)
  5. To make it really simple for you if your processor supports 64bit you can address or use more than 4GB of memory.

    If you have a 32bit processor or a 32bit OS and you put 8GB of RAM on the system than you will only be able to use 4GB (Windows will see about 3.2 to 3.4GB of the memory).

    Since the release of the Intel® Core™ 2 Duo everything in our desktop processor line up has supported 64bit (except maybe some of the early Intel Atom™ processors).

    Christian Wood
    Intel Enthusiast Team
  6. 64 bit processing is more than that of ram support, even we can use all ram on 32 bit system with tweaks, and some boards are also able to make use of all ram on 32 bit os

    and it is not related to variables used in programming
  7. not all cpu's support 64bit some are still about that are only 32bit. the reason that they advertise 64bit support is that it easily helps the end user identify the product as able to use a 64bit o.s. yes to programmers it means other things like bigger addressable area and so on, but for joe public it just helps cut through the sales crap.
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