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What we are getting if someone says "my machine is 64-bit computer" . What is the difference between 64-bit computer (I mean the CPU architecture) and operating system (Windows 64-bit OS). Please explain me how these terms are related with processor architecture.

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A 64-bit processor is one which handles (or can handle) 64 bits of data in a single operation (for example addition of two registers each containing 64-bit integers, or accessing a memory location via a 64-bit pointer).

A 64-bit operating system is one which is compiled to take advantage of the 64-bit instructions provided by a 64-bit processor and as such will not work on a processor that does not support these instructions. One advantage of 64-bit Windows for example is that it can take advantage of more physical RAM than the 32-bit version of Windows.

Many mainstream 64-bit processors also have 32-bit instructions so that they are able to run either a 32-bit or a 64-bit operating system.

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    I would like to further add that most 64-bit operating systems can run 32-bit code. They still require 64-bit drivers, however. Oct 10, 2010 at 9:06
  • Also, there are 64-bit chips that can't run 32-bit code without emulation (such as Itaniums) as well as 64-bit chips that can run 32-bit code but must run a 64-bit OS (such as some SPARC architectures). However, neither shows up in processors that can really be considered "mainstream". Oct 10, 2010 at 9:43
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CPU with 64-bit registers can process more data than the 32-bit CPU that is faster than the CPU 16-bit and 8-bit. The more space available in the system CPU registers, the more also the process that can be handled, particularly in terms of system memory

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    Often the wider registers will result in poorer performance. And address space is only loosely associated with register size. It all depends on the internal CPU architecture. Jun 27, 2012 at 2:10
  • any Documentation?
    – Malachi
    Oct 19, 2012 at 22:00

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