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Intel 5-level paging, referred to simply as 5-level paging in Intel documents, is a processor extension for the x86-64 line of processors. [1]: 11 It extends the size of virtual addresses from 48 bits to 57 bits by adding an additional level to x86-64's multilevel page tables, increasing the addressable virtual memory from 256 TiB to 128 PiB.
For some processors, a mode can be enabled with a fifth table, the 512-entry page-map level 5 table; this means that 57 bits of virtual page number are translated, giving a virtual address space of up to 128 PB. [10]: 141–153 In the page table entries, in the original specification, 40 bits of physical page number are implemented.
See Intel 64 and IA-32 Architectures Software Developer's Manual. 23: CET: Control-flow Enforcement Technology: If set, enables control-flow enforcement technology. [16]: 2–19 24: PKS: Enable Protection Keys for Supervisor-Mode Pages: If set, each supervisor-mode linear address is associated with a protection key when 4-level or 5-level ...
The page-directory entry with PS set to 0 behaves as without PSE. If newer PSE-36 capability is available on the CPU, as checked using the CPUID instruction, then 4 more bits, in addition to normal 10 bits, are used inside a page-directory entry pointing to a large page. This allows a large page to be located in 36-bit address space.
The general operation of the segmentation unit is otherwise unchanged. The paging unit may be enabled or disabled; if disabled, operation is the same as on the 80286. If the paging unit is enabled, addresses in a segment are now virtual addresses, rather than physical addresses as they were on the 80286.
A 68451 MMU, which could be used with the Motorola 68010. A memory management unit (MMU), sometimes called paged memory management unit (PMMU), [1] is a computer hardware unit that examines all memory references on the memory bus, translating these requests, known as virtual memory addresses, into physical addresses in main memory.
In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.
The Global Descriptor Table (GDT) is a data structure used by Intel x86-family processors starting with the 80286 in order to define the characteristics of the various memory areas used during program execution, including the base address, the size, and access privileges like executability and writability.