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Physical Address
In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a ''particular'' storage cell of main memory, or a register of memory-mapped I/O device. Use by central processing unit In a computer supporting virtual memory, the term ''physical address'' is used mostly to differentiate from a '' virtual address''. In particular, in computers utilizing a memory management unit (MMU) to translate memory addresses, the virtual and physical addresses refer to an address before and after translation performed by the MMU, respectively. Unaligned addressing Depending upon its underlying computer architecture, the performance of a computer may be hindered by ''unaligned'' access to memory. For example, a 16-bit computer with a 16-bit memory data bus, such as Intel 8086, generally has less overhead if the access is aligned to an even ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Address Space And Physical Address Space Relationship
Virtual may refer to: * Virtual image, an apparent image of an object (as opposed to a real object), in the study of optics * Virtual (horse), a thoroughbred racehorse * Virtual channel, a channel designation which differs from that of the actual radio channel (or range of frequencies) on which the signal travels * Virtual function, a programming function or method whose behaviour can be overridden within an inheriting class by a function with the same signature * Virtual machine, the virtualization of a computer system * Virtual meeting, or web conferencing * Virtual memory, a memory management technique that abstracts the memory address space in a computer * Virtual particle, a type of short-lived particle of indeterminate mass * Virtual reality (virtuality), computer programs with an interface that gives the user the impression that they are physically inside a simulated space * Virtual world, a computer-based simulated environment populated by many users who can create a persona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorola 68010
The Motorola MC68010 and Motorola MC68012 are 16/32-bit microprocessor, microprocessors from Motorola, released in 1982 as successors to the Motorola 68000. The 68010 and 68012 added virtualization features, optimized loops and fixed several small flaws to the 68000. The MC68010 variants were Pin compatibility, pin compatible with its predecessor while the MC68012 is an 84-pin pin grid array, PGA version with its directly accessible memory space extended to 2 gigabyte, GiB. Differences between 68010/68012 and 68000 The 68010 and 68012 are completely user-mode compatible with the 68000, except that the MOVE from SR instruction traps in user mode, so that, to support user-mode code using that instruction, a supervisor-mode trap handler must simulate the instruction and continue the user-mode code after that instruction. This was done so that the 68010 and 68012 would meet the Popek and Goldberg virtualization requirements, specifically that a new OS could run as guest and no ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Storage
Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but less expensive and larger options further away. Generally, the fast technologies are referred to as "memory", while slower persistent technologies are referred to as "storage". Even the first computer designs, Charles Babbage's Analytical Engine and Percy Ludgate's Analytical Machine, clearly distinguished between processing and memory (Babbage stored numbers as rotations of gears, while Ludgate stored numbers as displacements of rods in shuttles). This distinction was extended in the Von Neumann architecture, whe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pointer (computer Programming)
In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer ''references'' a location in memory, and obtaining the value stored at that location is known as ''dereferencing'' the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture. Using pointers significantly improves performance for repetitive operations, like traversing iterable data structures (e.g. strings, lookup tables, control tables, linked lists, and tree structures). In particular, it is often much cheaper in time and space to copy and deref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page Address Register
A page address register (PAR) contains the physical addresses of pages currently held in the main memory of a computer system. PARs are used in order to avoid excessive use of an address table in some operating systems. A PAR may check a page's number against all entries in the PAR simultaneously, allowing it to retrieve the pages physical address quickly. A PAR is used by a single process and is only used for pages which are frequently referenced (though these pages may change as the process's behaviour changes in accordance with the principle of locality). An example computer which made use of PARs is the Atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio .... See also * Translation Lookaside Buffer (TLB) References Virtual memory Computer memory {{Comp-sci-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Address Space
In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity. For software programs to save and retrieve stored data, each datum must have an address where it can be located. The number of address spaces available depends on the underlying address structure, which is usually limited by the computer architecture being used. Often an address space in a system with virtual memory corresponds to a highest level translation table, e.g., a segment table in IBM System/370. Address spaces are created by combining enough uniquely identified qualifiers to make an address unambiguous within the address space. For a person's physical address, the ''address space'' would be a combination of locations, such as a neighborhood, town, city, or country. Some elements of a data address space may be the same, but if any element in the address is different, ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Addressing Mode
Addressing modes are an aspect of the instruction set architecture in most central processing unit (CPU) designs. The various addressing modes that are defined in a given instruction set architecture define how the machine language instructions in that architecture identify the operand(s) of each instruction. An addressing mode specifies how to calculate the effective memory address of an operand by using information held in registers and/or constants contained within a machine instruction or elsewhere. In computer programming, addressing modes are primarily of interest to those who write in assembly languages and to compiler writers. For a related concept see orthogonal instruction set which deals with the ability of any instruction to use any addressing mode. Caveats There are no generally accepted names for addressing modes: different authors and computer manufacturers may give different names to the same addressing mode, or the same names to different addressing modes. F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Address Constant
{{short description, Assembly language data type In IBM System/360 through present day z/Architecture, an address constant or "adcon" is an assembly language data type which contains the address of a location in computer memory. An address constant can be one, two, three or four bytes long, although an adcon of less than four bytes is conventionally used to hold an expression for a small integer such as a length, a relative address, or an index value, and does not represent an address at all. Address constants are defined using an assembler language "DC" statement. Other computer systems have similar facilities, although different names may be used. Types of address constants A adcons normally store a four byte relocatable address, however it is possible to specify the length of the constant. For example, AL1(stuff) defines a one-byte adcon, useful mainly for small constants with relocatable values. Other adcon types can similarly have length specification. V type adcons store a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Device Driver
In the context of an operating system, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and other computer programs to access hardware functions without needing to know precise details about the hardware being used. A driver communicates with the device through the computer bus or communications subsystem to which the hardware connects. When a calling program invokes a routine in the driver, the driver issues commands to the device (drives it). Once the device sends data back to the driver, the driver may invoke routines in the original calling program. Drivers are hardware dependent and operating-system-specific. They usually provide the interrupt handling required for any necessary asynchronous time-dependent hardware interface. Purpose The main purpose of device drivers is to provide abstraction b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mother Board
A motherboard, also called a mainboard, a system board, a logic board, and informally a mobo (see "Nomenclature" section), is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the CPU, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use. Nomenclature ''Oxford English Dictionary'' traces the origin of the word ''motherboard'' to 1965, its earliest-found attestation occurring in the magazine ''Electronics''. The term alludes to its importance and size compared to the components attached to it, being the "mother of all boards" in a computer system. A number of gender-neutral alternat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Direct Memory Access
Direct memory access (DMA) is a feature of computer systems that allows certain hardware subsystems to access main system computer memory, memory independently of the central processing unit (CPU). Without DMA, when the CPU is using programmed input/output, it is typically fully occupied for the entire duration of the read or write operation, and is thus unavailable to perform other work. With DMA, the CPU first initiates the transfer, then it does other operations while the transfer is in progress, and it finally receives an interrupt from the DMA controller (DMAC) when the operation is done. This feature is useful at any time that the CPU cannot keep up with the rate of data transfer, or when the CPU needs to perform work while waiting for a relatively slow I/O data transfer. Many hardware systems use DMA, including disk drive controllers, graphics cards, network cards and sound cards. DMA is also used for intra-chip data transfer in some multi-core processors. Computers that h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
