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Rearranged a few sentences in the beginning and fixed some typos.
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(Table 4-6, chapter 4, section 4.3 of the Intel IA64 and IA32 Architecture's Software Developer's Manual, volume 3 states that it should not necessarily be 0 if PAT is supported.) |
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[[image:Paging_Structure.gif|right|thumb|600x350px|x86 Paging Structure]]
Paging is a system which allows each process to see a full virtual address space, without actually requiring the full amount of physical memory to be available or present. 32-bit x86 processors support 32-bit virtual addresses and 4-GiB virtual address spaces, and current 64-bit processors support 48-bit virtual addressing and 256-TiB virtual address spaces
In addition to this, paging introduces the benefit of page-level protection. In this system, user processes can only see and modify data which is paged in on their own address space, providing hardware-based isolation. System pages are also protected from user processes. On the x86-64 architecture, page-level protection now completely supersedes [[Segmentation]] as the memory protection mechanism. On the IA-32 architecture, both paging and segmentation exist, but segmentation is now considered 'legacy'.
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