Expanded Memory Specification definition storage
(EMS) An IBM PC
scheme enabling access to memory other than conventional memory
in real mode
. Expanded memory
is provided through a page frame of at least 64 kilobytes
in the reserved memory
address region. Access to this memory is provided by an expanded memory manager
(EMM) software. The EMM functions are accessible through interrupt
based systems this is the only way to use memory beyond conventional memory. In systems based on 80286
or later, XMS
provide alternative methods.
EMS was developed jointly by Lotus
, and Microsoft
prior to 1988. Accordingly, this specification is sometimes referred to as LIM EMS.
A complete discussion of EMS and programming examples can be found in ["PC System Programming for developers", 1989, ISBN 1-55755-035-2 (Book only) and ISBN 1-55755-036-0 (Book and diskette)]. EEMS
, a competing expanded memory management standard, was developed by AST Research, Quadram and Ashton-Tate.
See also upper memory block