Expanded Memory Specification

storage (EMS) An IBM PC memory paging scheme enabling

access to memory other than conventional memory in realmode.

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 memorymanager (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.

(1996-01-10)