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PAE was first introduced by Intel in the Pentium Pro, and later by AMD in the Athlon processor. [2] It defines a page table hierarchy of three levels (instead of two), with table entries of 64 bits each instead of 32, allowing these CPUs to directly access a physical address space larger than 4 gigabytes (2 32 bytes).
The 32-bit PAE desktop kernel (linux-image-generic-pae) in Ubuntu 9.10 and later, also provides the PAE mode needed for hardware with the NX CPU feature. For systems that lack NX hardware, the 32-bit kernels now provide an approximation of the NX CPU feature via software emulation that can help block many exploits an attacker might run from ...
Many x86 operating systems, including any version of Linux with a PAE kernel and some versions of Windows Server and macOS, can use PAE to address up to 64 GiB of memory on an x86 system. [8] [9] [10] There are other factors that may limit this ability to use up to 64 GiB of memory, and lead to the "3 GB barrier" under certain circumstances ...
The NX bit (no-execute) is a technology used in CPUs to segregate areas of a virtual address space to store either data or processor instructions. An operating system with support for the NX bit may mark certain areas of an address space as non-executable. The processor will then refuse to execute any code residing in these areas of the address ...
To address a PCI device, it must be enabled by being mapped into the system's I/O port address space or memory-mapped address space. The system's firmware (e.g. BIOS ) or the operating system program the Base Address Registers (commonly called BARs) to inform the device of its resources configuration by writing configuration commands to the PCI ...
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.
Compared to the Physical Address Extension (PAE) method, PSE-36 is a simpler alternative to addressing more than 4 GB of memory. It uses the Page Size Extension (PSE) mode and a modified page directory table to map 4 MB pages into a 64 GB physical address space. PSE-36's downside is that, unlike PAE, it doesn't have 4-KB page granularity above ...
4-level paging of the 64-bit mode. In the 4-level paging scheme (previously known as IA-32e paging), the 64-bit virtual memory address is divided into five parts. The lowest 12 bits contain the offset within the 4 KiB memory page, and the following 36 bits are evenly divided between the four 9 bit descriptors, each linking to a 64-bit page table entry in a 512-entry page table for each of the ...