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From: kjeld@iesd.dk (Kjeld Flarup)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: More than 640k on a 286
Message-ID: <2072@iesd.dk>
Date: 15 Jun 89 11:14:30 GMT
References: <1177@draken.nada.kth.se>
Reply-To: kjeld@iesd.dk (Kjeld Flarup)
Organization: Dept. of Comp. Sci., Aalborg University, Denmark
Lines: 33

In article <1177@draken.nada.kth.se> d87-psk@nada.kth.se (Patrik Skottsborg) writes:
>I'm looking for a public domain or shareware program that will break
>the AT's 640k limit. I am NOT talking about normal EMS- or XMS-extention here.
>There exist a comercial product called 'MAX 386' which uses your expanded
>or extended memory to bring up the '640k' block to >752k on a 386-machine
> (using some 386-cpu feature). Is it possible to do something like this
>on a 286-machine ?

Both yes and no. Normally the video RAM splits a 1Mb AT into at 640Kb DOS
and then the rest is put into EMS.

But however there is a gab between the video RAM and BIOS ROM. I have seen
a program called himen which is able to load resident programs into RAM
located in that part of the memory. These programs could be keyboard drivers
or even sidekick. Thus it is possible to release more memory to DOS
applications.

To do this trick on a 80386 machine is no problem, bacause of the MMU.
But on the 80286 there must be memory between video and BIOS. Some AT
machines mirrors the EMS into that area. If you want to test this try
this little Turbo Pascal line

var
  teststring: string at $e000:0000;

If you can work normally on this you may be able to use himem. Note that I
haven't testet this, and there could be a conflict with EMS that causes the 
machine to crash.


-- 
Kjeld Flarup Christensen | "I'am now thirty-seven times older than the universe
kjeld@iesd.dk            | itself." Marvin the depressed Robot.