jal@valhalla.ee.rochester.edu (11/23/88)
Extended vs Expanded Memory The generally accepted definition is that extended memory is that memory which is addressed above 1 MByte on a PC like machine. Note that most 286/386 systems which come with "1 Meg on the motherboard" have 384K of extended memory (there are exceptions to this). Expanded memory is essentially bank switched memory which conforms to a EMS (or EEMS) specification. The most popular is the LIM EMS (now 4.0) spec. Also AQA EEMS is a form of expanded memory (For the most part the functionality of EEMS has been incorporated in EMS 4.0) There are programs which allow you to treat (for the most part) extended memory as expanded memory. Some of the programs which are specific to 386 or PS/2 50-60's are true (or nearly true) expanded memory providers. Some which run on any PC or clone (they can often make a disk file look like EMS memory) suffer both from performance and from an inability to correctly emulate some capabilities of EMS. For many applications these limitations are not important, but for some they are. I am the author of a commercial program which does this and so I am not a completely disinterested party. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - I program ... therefore I am. John Lefor University of Rochester Dept of E. Engineering 716-275-8265 jal@ee.rochester.edu uunet!ur-valhalla!jal