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Extended Feature Enable Register (EFER) is a model-specific register added in the AMD K6 processor, to allow enabling the SYSCALL/SYSRET instruction, and later for entering and exiting long mode. This register becomes architectural in AMD64 and has been adopted by Intel as IA32_EFER.
From CR3, the page table walker can access page directories and tables that are beyond the 32-bit range. Secondly, the physical address for the data being accessed (stored in the page table) can be represented as a physical address larger than the 32-bit addresses supported in a system without PAE.
The entries in the page directory have an additional flag, in bit 7, named PS (for page size). This flag was ignored without PSE, but now, the page-directory entry with PS set to 1 does not point to a page table, but to a single large 4 MiB page. The page-directory entry with PS set to 0 behaves as without PSE.
For another example, in the Intel Pentium Pro, the page global enable (PGE) flag in the register CR4 and the global (G) flag of a page-directory or page-table entry can be used to prevent frequently used pages from being automatically invalidated in the TLBs on a task switch or a load of register CR3.
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.
A hardware page table walker can treat the additional translation layer almost like adding levels to the page table. Using SLAT and multilevel page tables, the number of levels needed to be walked to find the translation doubles when the guest-physical address is the same size as the guest-virtual address and the same size pages are used.
A process can store data in memory-mapped files on memory-backed file systems, such as the tmpfs file system or file systems on a RAM drive, and map files into and out of the address space as needed. A set of processes may still depend upon the enhanced security features page-based isolation may bring to a multitasking environment.
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.