XMS (eXtended Memory Specification) Unit For Turbo Pascal 6.0
Version 1.0
Written by Yuval Tal
04-Mar-91
This program may be freely distributed for non-commercial, non-business,
and non-governmental uses, provided this notice is attached with it. My
only request is that if you plan to use it regularly, let me know of know
about it through e-mail or postal mail, so that I have an idea of how useful
this program is (if you will add some cash to that letter it would be nice,
ofcourse :-)). Also, if you have any problems, suggestions etc' please let
me know.
InterNet:
nyyuval@weizmann.weizmann.ac.il
or
yuvalt@wisdocs.weizmann.ac.il
Home address:
13 Glazer st.
Rehovot, 76283
Israel
Introduction
------------
The primitive method of accessing the extended memory is by using the AT's
BIOS interrupt 15h. These methods have several weaknesses which I will not
describe here. At 1988 Microsoft, Intel, AST Research and Lotus Corp. made
a more sophisticated use of extended memory under MS-DOS - eXtended Memory
Specification (XMS). The XMS defines software interface for 80286, 80386
and 80486 based PCs that allow real-mode application to use extended memory
(EMB) and some areas of conventional memory which MS-DOS does not manage
(UMB and HMA). Here is a figure which descirbes the memory:
+-----------------+ 0K \
| | |
| Base Memory | |
| | | Conventional Memory
| | |
+-----------------+ 640K |
| Upper
|