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Revision as of 06:45, 27 February 2017

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Added mention of Intel's "57-bit virtual addressing" extension
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m (Added mention of Intel's "57-bit virtual addressing" extension)
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[[image:Paging_Structure.gif|right|thumb|600x350px|x86 Paging Structure]]
 
32-bit x86 processors support a32-bit virtual addresses and 4-GiB virtual address spacespaces, and current 64-bit processors support a48-bit virtual addressing and 256-TiB virtual address spacespaces; (withand Intel have released documentation for a theoreticalplanned maximumextension ofto 1657-bit EiB)virtual addressing and 128-PiB virtual address spaces. Paging is a system which allows each process to see thea full virtual address space, without actually requiring the full amount of physical memory to be available or present. In fact, current implementations of x86-64 have a limit of 1between 4 GiB and 256 TiB of physical address space (and aan theoreticalarchitectural limit of 4 PiB of physical RAMaddress space).
 
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'.
Brendan
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