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Extended memory refers to memory above the first megabyte of address space in an IBM PC with an 80286 or later processor. This article does not cite any references or sources. ...
ReBoot character, see Megabyte (ReBoot). ...
In computing, an address space defines a range of discrete addresses, each of which may correspond to a physical or virtual memory register, a network host, peripheral device, disk sector or other logical or physical entity. ...
IBM PC (IBM 5150) with keyboard and green screen monochrome monitor (IBM 5151), running MS-DOS 5. ...
The Intel 80286 is an x86-family 16-bit microprocessor that was introduced by Intel on February 1, 1982. ...
CPU redirects here. ...
Extended memory is only available on PC's based on the Intel 80286 or higher processor. Only these chips can address more than 1 MB of RAM. The earlier 8086/8088 processors can make use of more than 1 MB of RAM if one employs special hardware to make selectable parts of it appear at addresses below 1 MB, but this does not constitute extended memory as defined in this article. Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is an American multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ...
The Intel 80286 is an x86-family 16-bit microprocessor that was introduced by Intel on February 1, 1982. ...
MB, Mb, mB or mb may mean: Mb (digraph) Megabit (1,000,000 bits) or mebibit (220 = 1,048,576 bits); the preferred symbols are Mb and Mibit, respectively¹ Megabyte (1,000,000 bytes) or mebibyte (220 = 1,048,576 bytes); the preferred symbols are MB and MiB, respectively¹ MB...
Look up RAM, Ram, ram in Wiktionary, the free dictionary. ...
On a 286 or better PC equipped with more than 640 KB of RAM, the additional memory would generally be re-mapped above the 1 MB boundary, since the IBM PC architecture mandates a 384 KB "hole" in memory between the 640 KB and 1 MB boundaries. This way all of the additional memory would be available to programs running in Protected mode. Even without such remapping, machines with more than 1 MB of RAM would have access to memory above 1 MB. The abbreviation KB or kb can refer to: kilobyte (kB or KB), equal to 1,000 bytes or 1024 bytes depending on context, or kibibyte (KiB), equal to 1,024 bytes. ...
Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ...
Extended memory is available in real mode only through EMS, UMB, XMS, or HMA; only applications executing in protected mode can use extended memory directly. In this case, the extended memory is provided by a supervising protected-mode operating system such as Microsoft Windows. The processor makes this memory available through the Global Descriptor Table and one or more Local Descriptor Tables (LDTs). The memory is "protected" in the sense that memory segments assigned a local descriptor cannot be accessed by another program because that program uses a different LDT, and memory segments assigned a global descriptor can have their access rights restricted, causing a hardware trap (typically a General Protection Fault) on violation. This prevents programs running in protected mode from interfering with each other's memory. Real mode (also called real address mode in Intels manuals) is an operating mode of 80286 and later x86-compatible CPUs. ...
Expanded Memory was a trick invented around 1984 that provided more memory to byte-hungry, business-oriented MS-DOS programs. ...
The Upper Memory Area (UMA) is a feature of the design of IBM PC-compatible x86 computers. ...
The High Memory Area (HMA) is the RAM area consisting of the first 64 kibibytes (KiB), minus 16 bytes, of the extended memory on an IBM PC or compatible microcomputer. ...
Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ...
An operating system (OS) is the software that manages the sharing of the resources of a computer and provides programmers with an interface used to access those resources. ...
Windows redirects here. ...
The Global Descriptor Table or GDT is a data structure used by Intel x86-family processors starting with the 80286 in order to define the characteristics of the various memory areas used during program execution, for example the base address, the size and access privileges like executability and writability. ...
The Local Descriptor Table (LDT) is a memory table used in the x86 architecture in protected mode and containing memory segment descriptors: start in linear memory, size, executability, writability, access privilege, actual presence in memory, etc. ...
A General Protection Fault (GPF) in the Intel x86 and AMD x86-64 architectures is a fault (a type of an interrupt) which can encompass several cases, where protection mechanisms within the processor architecture are violated by any of the programs that is running, whether it be the kernel or...
A protected-mode operating system such as Windows can also run real-mode programs and provide expanded memory to them. The DOS Protected Mode Interface is Microsoft's prescribed method for an MS-DOS program to access extended memory under a multitasking environment. Expanded Memory was a trick invented around 1984 that provided more memory to byte-hungry, business-oriented MS-DOS programs. ...
DPMI is the method which Microsoft prescribes for a DOS program to run in protected mode and to access extended memory under a multitasking operating system like Microsoft Windows 3. ...
Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ...
In computing, multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is...
Extended Memory Specification Extended Memory Specification or XMS is the specification describing the use of IBM PC extended memory in real mode for storing data (but not for running executable code in it). Memory is made available by extended memory manager (XMM) software such as HIMEM.SYS. The XMM functions are accessible through interrupt 2Fh. XMS should not be confused with the somewhat similar EMS (expanded memory specification). IBM PC (IBM 5150) with keyboard and green screen monochrome monitor (IBM 5151), running MS-DOS 5. ...
Real mode (also called real address mode in Intels manuals) is an operating mode of 80286 and later x86-compatible CPUs. ...
HIMEM is a DOS device driver which allows DOS programs to store data in extended memory via the Extended Memory Specification (XMS). ...
Expanded Memory was a trick invented around 1984 that provided more memory to byte-hungry, business-oriented MS-DOS programs. ...
See also Unreal mode, also big real mode, huge real mode, or flat real mode, is a variant of real mode (PE=0), in which one or more data segment registers have been loaded with 32-bit addresses and limits. ...
Conventional memory is the first 640 kibibytes of an IBM PCs memory. ...
The Upper Memory Area (UMA) is a feature of the design of IBM PC-compatible x86 computers. ...
Expanded Memory was a trick invented around 1984 that provided more memory to byte-hungry, business-oriented MS-DOS programs. ...
The High Memory Area (HMA) is the RAM area consisting of the first 64 kibibytes (KiB), minus 16 bytes, of the extended memory on an IBM PC or compatible microcomputer. ...
References - This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
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