Techniques employed to give applications access to more than 640 kibibytes
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This article is about the DOS operating systems. For the general concept, see memory management.
Physical memory areas of the IBM PC family
In IBM PC compatible computing, DOS memory management refers to software and techniques employed to give applications access to more than 640 kibibytes (640*1024 bytes) (KiB) of "conventional memory". The 640 KiB limit was specific to the IBM PC and close compatibles; other machines running MS-DOS had different limits, for example the Apricot PC could have up to 768 KiB and the Sirius Victor 9000, 896 KiB. Memory management on the IBM family was made complex by the need to maintain backward compatibility to the original PC design[1] and real-mode DOS, while allowing computer users to take advantage of large amounts of low-cost memory and new generations of processors. Since DOS has given way to Microsoft Windows and other 32-bit operating systems not restricted by the original arbitrary 640 KiB limit of the IBM PC, managing the memory of a personal computer no longer requires the user to manually manipulate internal settings and parameters of the system.
The 640 KiB limit imposed great complexity on hardware and software intended to circumvent it; the physical memory in a machine could be organised as a combination of base or conventional memory (including lower memory), upper memory, high memory (not the same as upper memory), extended memory, and expanded memory, all handled in different ways.
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In IBM PC compatible computing, DOSmemorymanagement refers to software and techniques employed to give applications access to more than 640 kibibytes...
In DOSmemorymanagement, extended memory refers to memory above the first megabyte (220 bytes) of address space in an IBM PC or compatible with an 80286...
In DOSmemorymanagement, the upper memory area (UMA) is the memory between the addresses of 640 KB and 1024 KB (0xA0000–0xFFFFF) in an IBM PC or compatible...
In DOSmemorymanagement, expanded memory is a system of bank switching that provided additional memory to DOS programs beyond the limit of conventional...
In DOSmemorymanagement, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is...
DPMS may refer to: DOS Protected Mode Services, a set of extended DOSmemorymanagement services since 1992 VESA Display Power Management Signaling, a graphics...
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In DOSmemorymanagement, the high memory area (HMA) is the RAM area consisting of the first 65520 bytes above the one megabyte in an IBM AT or compatible...
of physical memory. PAE and 64-bit systems may be able to address up to the full address space of the x86 processor. DOSmemorymanagement Motherboard...
expanded memory manager of Microsoft's MS-DOS, IBM's PC DOS, Digital Research's DR-DOS, and Datalight's ROM-DOS which is used to create expanded memory using...
expanded memory manager in DOS (e.g. CEMM, QEMM, later EMM386) and does allow 80386 protected-mode DOS extenders to coexist with 80386 EMS expanded memory emulators...
DOS/360 from 1966. Others include Apple DOS, Apple ProDOS, Atari DOS, Commodore DOS, TRSDOS, and AmigaDOS. IBM PC DOS (and the separately sold MS-DOS)...
uses this feature (both 286 and 386 variants) to address extended memory, unless DOS is switched to run in a virtual 8086 mode that is incompatible with...
Extended VCPI (XVCPI) to make the memorymanagement and multitasking capabilities of the 386 available for extended DOS applications. When it turned out...
Services (VDS) refer to an application programming interface that allow DOS and Win16 applications and device drivers to perform DMA operations while...
64 KB of memory or less; it was designed to take a maximum of 640 KB. This rapidly became a restriction that had to be handled by complex DOSmemory management...
is an internal DOS command in COMMAND.COM that is used to load a program into the upper memory area (UMA) instead of conventional memory. The command was...
It was the most popular third-party memory manager for the MS-DOS and other DOS operating systems. QRAM A memory manager for Intel 80286 or higher CPUs...
Atari DOS is the disk operating system used with the Atari 8-bit computers. Operating system extensions loaded into memory were required in order for an...
virtual DOS monitor and paged memorymanagement Microsoft to Release Own DOS 3.3, InfoWorld, August 3, 1987 EMS Update Gives DOS Improved Multitasking, InfoWorld...
speculation that SR uses its own memory manager that accesses the MMU directly; in fact SR uses standard DOSmemorymanagement functions. The demo runs best...
intelligence character, and associated appearances Helix HeadRoom, DOSmemorymanagement software by Helix Software Company This disambiguation page lists...
with the Intel 80386), to cope with the memory limitations of DOS. A DOS extender is a program that "extends" DOS so that programs running in protected...
HeadRoom is a DOS context switching and multitasking memory manager produced by Helix Software Company in the late 1980s and early 1990s. HeadRoom managed...
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