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Page Attribute Table
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. Processors The PAT is available on Pentium III The Pentium III (marketed as Intel Pentium III Processor, informally PIII or P3) brand refers to Intel's 32-bit x86 desktop and mobile CPUs based on the sixth-generation P6 microarchitecture introduced on February 28, 1999. The brand's initial ... and newer CPUs, and on non-Intel CPUs. See also * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Processor Supplementary Capability
A processor supplementary capability is a feature that has been added to an existing central processing unit (CPU) design after the initial introduction of that design to the marketplace. A supplementary capability increases the usefulness of the processor design, allowing it to compete more favorably with competitors and giving consumers a reason to upgrade, while retaining backwards compatibility with the original design. The CPU supplementary instruction capability does not as a rule apply to 8 or 16 bit CPUs, as many of these CPUs are used mostly as microcontrollers. On modern 32 and 64 bit CPUs the ''processor supplementary capability'' does not extend to Floating Point Units (FPUs) or Memory Management Units (MMUs) as these are considered to be fundamental core functionalities. Extensions to the core functionalities of the MMU and FPU may be considered CPU extensions however. Historical reasoning The supplementary instructions feature has always been assumed to mean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 used by the program executed by the accessing process, while physical addresses are used by the hardware, or more specifically, by the random-access memory (RAM) subsystem. The page table is a key component of virtual address translation that is necessary to access data in memory. Role of the page table In operating systems that use virtual memory, every process is given the impression that it is working with large, contiguous sections of memory. Physically, the memory of each process may be dispersed across different areas of physical memory, or may have been moved ( paged out) to secondary storage, typically to a hard disk drive (HDD) or solid-state drive (SSD). When a process requests access to data in its memory, it is the responsibility of the operating system to map the virtual addres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X86-64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mode. With 64-bit mode and the new paging mode, it supports vastly larger amounts of virtual memory and physical memory than was possible on its 32-bit predecessors, allowing programs to store larger amounts of data in memory. x86-64 also expands general-purpose registers to 64-bit, and expands the number of them from 8 (some of which had limited or fixed functionality, e.g. for stack management) to 16 (fully general), and provides numerous other enhancements. Floating-point arithmetic is supported via mandatory SSE2-like instructions, and x87/ MMX style registers are generally not used (but still available even in 64-bit mode); instead, a set of 16 vector registers, 128 bits each, is used. (Each register can store one or two double-preci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Type Range Registers
Memory type range registers (MTRRs) are a set of processor supplementary capability control registers that provide system software with control of how accesses to memory ranges by the CPU are cached. It uses a set of programmable model-specific registers (MSRs) which are special registers provided by most modern CPUs. Possible access modes to memory ranges can be uncached, write-through, write-combining, write-protect, and write-back. In write-back mode, writes are written to the CPU's cache and the cache is marked dirty, so that its contents are written to memory later. Write-combining allows bus write transfers to be combined into a larger transfer before bursting them over the bus to allow more efficient writes to system resources like graphics card memory. This often increases the speed of image write operations by several times, at the cost of losing the simple sequential read/write semantics of normal memory. Additional bits which are provided on some computer arc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CPU Cache
A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, which stores copies of the data from frequently used main memory locations. Most CPUs have a hierarchy of multiple cache levels (L1, L2, often L3, and rarely even L4), with different instruction-specific and data-specific caches at level 1. The cache memory is typically implemented with static random-access memory (SRAM), in modern CPUs by far the largest part of them by chip area, but SRAM is not always used for all levels (of I- or D-cache), or even any level, sometimes some latter or all levels are implemented with eDRAM. Other types of caches exist (that are not counted towards the "cache size" of the most important caches mentioned above), such as the translation lookaside buffer (TLB) which is part of the memory management unit (MMU) w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page (computer Science)
A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in the page table. It is the smallest unit of data for memory management in a virtual memory operating system. Similarly, a page frame is the smallest fixed-length contiguous block of physical memory into which memory pages are mapped by the operating system. A transfer of pages between main memory and an auxiliary store, such as a hard disk drive, is referred to as paging or swapping. Page size trade-off Page size is usually determined by the processor architecture. Traditionally, pages in a system had uniform size, such as 4,096 bytes. However, processor designs often allow two or more, sometimes simultaneous, page sizes due to its benefits. There are several points that can factor into choosing the best page size. Page table size A system with a smaller page size uses more pages, requiring a page table that occupies more space. For example, if a 232 vi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of around 74.99%. macOS by Apple Inc. is in second place (14.84%), and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentium III
The Pentium III (marketed as Intel Pentium III Processor, informally PIII or P3) brand refers to Intel's 32-bit x86 desktop and mobile CPUs based on the sixth-generation P6 microarchitecture introduced on February 28, 1999. The brand's initial processors were very similar to the earlier Pentium II-branded processors. The most notable differences were the addition of the Streaming SIMD Extensions (SSE) instruction set (to accelerate floating point and parallel calculations), and the introduction of a controversial serial number embedded in the chip during manufacturing. The Pentium III is also a single-core processor. Even after the release of the Pentium 4 in late 2000, the Pentium III continued to be produced with new models introduced until early 2003, and were discontinued in April 2004 for desktop units, and May 2007 for mobile units. Processor cores Similarly to the Pentium II it superseded, the Pentium III was also accompanied by the Celeron brand for lower-end versions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write-combining
Write combining (WC) is a computer bus technique for allowing data to be combined and temporarily stored in a buffer the write combine buffer (WCB) to be released together later in burst mode instead of writing (immediately) as single bits or small chunks. Technique Write combining cannot be used for general memory access (data or code regions) due to the weak ordering. Write-combining does not guarantee that the combination of writes and reads is done in the expected order. For example, a write/read/write combination to a specific address would lead to the write combining order of read/write/write which can lead to obtaining wrong values with the first read (which potentially relies on the write before). In order to avoid the problem of read/write order described above, the write buffer can be treated as a fully associative cache and added into the memory hierarchy of the device in which it is implemented. Adding complexity slows down the memory hierarchy so this technique i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very large (main) memory". The computer's operating system, using a combination of hardware and software, maps memory addresses used by a program, called '' virtual addresses'', into ''physical addresses'' in computer memory. Main storage, as seen by a process or task, appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit (MMU), automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities, utilizing, e.g., disk storage, to provide a virtual address space that ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
