Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!uunet!mcsun!hp4nl!sci.kun.nl!jaaps
From: jaaps@dbf.kun.nl (Jaap Shane)
Newsgroups: comp.os.msdos.misc
Subject: Re: Does MSDOS 5.0 support Upper Memory on a 286?
Message-ID: <3701@wn1.sci.kun.nl>
Date: 26 Jun 91 08:15:29 GMT
References: <811@wa3wbu.UUCP> <1991Jun21.082150.11675@csc.canberra.edu.au> <46R4MKP@dri.com> <3464@crdos1.crd.ge.COM>
Sender: root@sci.kun.nl
Lines: 48

davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) writes:


>  I think you are confusing high memory with upper memory. High memory
>starts at FFFF:0000 and goes up, on both [23]86. UMA is between C000 and
>F000 (or maybe B000 is the manager is smart enough to sneak under the
>VGA). So on a 286 you get 64k for the DOS, but not the memory space for
>the UMA.

>  Since the 286 doesn't have the right hardware to do UMA, it would have
>to be faked in software. The software would take about as much space as
>it saved. No gain, so they didn't do it. I think you could do it in
>less, but that's the condition which prevails. You still save 64k, which
>would seem useful.

Most modern 286's with C&T or other chipsets actually do have the hardware
for upper memory access. Since there is no standard on this, you cannot make
a generic driver for it, as you can with a 386. However there does exist
a shareware package which provides access to the upper memory on many
286's with C&T or other chipsets. It's called LASTBYTE and it is available
as TLB-V119.ZIP on simtel20 and others. I've been using it for a year with 
MSDOS 4.01, and since a week with MSDOS 5.0. 

On my computer, a 20 MHz 286 with 2MB os memory, with LASTBYTE I can 
use the devicehigh and loadhigh features of MSDOS 5.0 to get up to 685Kb
of available conventional memory, by loading MSDOS high, loading all drivers
and TSR's high using either LASTBYTE's HIGHDRVR or HIGHTSR programs, and
its HIGHAPND program to reclaim the memory from A000 - B000, which my
Hercules board doesn't use, for conventional memory.

The good part is, it even works for non-MSDOS 5.0 users, although you lose 
about 40-50 K to MSDOS 4.01 or 30-40 K for MSDOS 3.3

>-- 
>bill davidsen	(davidsen@crdos1.crd.GE.COM -or- uunet!crdgw1!crdos1!davidsen)
>  GE Corp R&D Center, Information Systems Operation, tech support group
>  Moderator comp.binaries.ibm.pc and 386-users digest.

Jaap Shane
----------------------------+------------------------------------------------
Jaap Shane                  | Department of Physical Chemistry,
Internet : jaaps@sci.kun.nl | Catholic University of Nijmegen  
Bitnet   : U627008@HNYKUN11 | Toernooiveld, 6525ED, Nijmegen, The Netherlands
--
----------------------------+------------------------------------------------
Jaap Shane                  | Department of Physical Chemistry,
Internet : jaaps@sci.kun.nl | Catholic University of Nijmegen  
Bitnet   : U627008@HNYKUN11 | Toernooiveld, 6525ED, Nijmegen, The Netherlands