Page Attribute Table
Encyclopedia
The page attribute table (PAT) is a processor supplementary capability
extension to the page table
format of certain x86 and x86-64
microprocessors. Like memory type range registers
(MTRRs), they allow for fine-grained control over how areas of memory are cached
, and are a companion feature to the MTRRs.
Unlike MTRRs, which provide the ability to manipulate the behavior of caching for a limited number of fixed physical address ranges, Page Attribute Tables allow for such behavior to be specified on a per-page basis, greatly increasing the ability of the operating system
to select the most efficient behavior for any given task.
Processor supplementary capability
A processor supplementary capability is a feature that has been added to an existing central processing unit design after the initial introduction of that design to the marketplace....
extension to the page table
Page table
A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are those unique to the accessing process...
format of certain x86 and x86-64
X86-64
x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...
microprocessors. Like memory type range registers
Memory Type Range Registers
Memory type range registers are a set of processor supplementary capabilities control registers that provide system software with control of how accesses to memory ranges by the CPU are cached...
(MTRRs), they allow for fine-grained control over how areas of memory are cached
CPU cache
A CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations...
, and are a companion feature to the MTRRs.
Unlike MTRRs, which provide the ability to manipulate the behavior of caching for a limited number of fixed physical address ranges, Page Attribute Tables allow for such behavior to be specified on a per-page basis, greatly increasing the ability of the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
to select the most efficient behavior for any given task.
External links
- Intel 64 and IA-32 Architectures Software Developer's Manual Volume 3A: System Programming Guide, Part 1 see chapter 11, section 12.