Expanded Memory Specification
<storage> (EMS) An
IBM PC memory
paging 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 67H.
In
8086 or
8088 based systems this is the only way to use memory beyond conventional memory.
In systems based on
80286 or later,
XMS and
HMA provide alternative methods.
EMS was developed jointly by Lotus, Intel, 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.
