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From: jca@pnet01.cts.com (John C. Archambeau)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Extended Memory
Message-ID: <4204@crash.cts.com>
Date: 16 May 89 02:36:56 GMT
Sender: news@crash.cts.com
Organization: People-Net [pnet01], El Cajon CA
Lines: 42

Under MesS-DOS, you have very few options with extended memory.  Here one the
ones that I know about;
 
1. Use a device driver to bump your remaining device drivers into extended
   memory.  I have this driver called HIMEM.SYS in my CONFIG.SYS, it is
   the first device driver that is loaded in, and what it does is set up
   all drivers loaded in after it to go into extended memory.
 
2. Use it as a ramdisk.

3. Find those mythical device drivers (I have yet to see one for myself)
   that converts extended memory to expanded.
 
4. Use some black magic and use the extended memory for your own programs.
   This can be done with AT BIOS int 15h, func 87h.  This is an extended
   memory block move routine.
 
As for extended vs. expanded.  Here are the differences in a brief summary.
 
   Extended memory is part of the '286 and '386 protected mode memory scheme.
   The 80286 can access up to 16 Mb of memory while in '286 protect mode.  
   Anything that's above the first 1 Mb of base memory (the uppermost 384K
   on the 8086/8 is reserved for ROM) is part of this memory scheme.
 
   Expanded memory is a standard specification for external memory beyond
   the 1 Mb of addressible memory for the 8086/8 processor.  The current
   specification is LIM EMS 4.0.  This is basically a page flipping scheme
   for external memory to an 80x86 processor in 8086 mode.  If you get an
   expanded memory card, make SURE that it supports the EMS 4.0 specification
   otherwise you will have wasted your money.  There are some EMS 3.2 cards
   out there, but they aren't really compatable with anything anymore.
   Also, DOS works VERY nicely with expanded memory.  Since the EMS memory
   appears in an window in the 640K base, DOS is very happy to work with
   it.  The page flipping is done very quickly and efficiently under EMS
   4.0
 
 JCA


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