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Groups > comp.os.msdos.programmer > #652

Re: Loading DOS high on a XT

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Ruud  <Ruud.Baltissen@apg.nl> wrote:
>DOS itself can be loaded high as well and AFAIk this is done by
>HIMEM.SYS. But that program won't work on a XT so the obvious
>question: how can I persuade DOS to load itself in the UMB area
>instead below the 640 KB barrier?

MS-DOS loads itself "high" (ie. DOS=HIGH in CONFIG.SYS) by loading part
of itself into the HMA (High Memory Area).  That's the (almost) 64K
area above the 20-bit addressing limit of the original 8086 CPU which
can be accessed from real mode on CPUs with more than 20-bit addressing
('286 or later).

Since the HMA doesn't exist on PC XTs you won't be able to convince
MS-DOS to load there.  If I can recall correctly, MS-DOS can also load
some code into UMBs, but I think that's limited to internal drivers and
parts of COMMAND.COM.  I assume you've already created an XMS driver
with UMB extensions to get your drivers loaded there.  If that doesn't
also convince MS-DOS to load what it can into UMBs, then I'm not sure
anything else will.

					Ross Ridge

-- 
 l/  //	  Ross Ridge -- The Great HTMU
[oo][oo]  rridge@csclub.uwaterloo.ca
-()-/()/  http://www.csclub.uwaterloo.ca/~rridge/ 
 db  //	  

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Thread

Loading DOS high on a XT Ruud <Ruud.Baltissen@apg.nl> - 2012-07-15 23:16 -0700
  Re: Loading DOS high on a XT Ross Ridge <rridge@csclub.uwaterloo.ca> - 2012-07-16 02:58 -0400
  Re: Loading DOS high on a XT "Rod Pemberton" <do_not_have@notemailnot.cmm> - 2012-07-16 05:10 -0400
    Re: Loading DOS high on a XT Ruud <Ruud.Baltissen@apg.nl> - 2012-07-17 01:37 -0700
      Re: Loading DOS high on a XT Jim Leonard <mobygamer@gmail.com> - 2012-07-17 14:11 -0700
        Re: Loading DOS high on a XT Ruud <Ruud.Baltissen@apg.nl> - 2012-07-17 22:36 -0700
  Re: Loading DOS high on a XT T. Ment <t.ment@protocol.invalid> - 2019-03-30 04:58 +0000
    Re: Loading DOS high on a XT "R.Wieser" <address@not.available> - 2019-03-30 08:04 +0100
      Re: Loading DOS high on a XT src153 <src153@protocol.invalid> - 2019-03-30 15:17 +0000
        Re: Loading DOS high on a XT "R.Wieser" <address@not.available> - 2019-03-30 19:30 +0100
          Re: Loading DOS high on a XT src153 <src153@protocol.invalid> - 2019-03-30 18:56 +0000
            Re: Loading DOS high on a XT "R.Wieser" <address@not.available> - 2019-03-30 21:18 +0100
              Re: Loading DOS high on a XT src153 <src153@protocol.invalid> - 2019-03-30 21:22 +0000
                Re: Loading DOS high on a XT src153 <src153@protocol.invalid> - 2019-03-30 23:09 +0000
                Re: Loading DOS high on a XT src153 <src153@protocol.invalid> - 2019-03-30 23:34 +0000
                Re: Loading DOS high on a XT "R.Wieser" <address@not.available> - 2019-03-31 10:25 +0200
        Re: Loading DOS high on a XT Rod Pemberton <invalid@lkntrgzxc.com> - 2019-04-02 18:05 -0400

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