Date: Tue, 19 May 1998 15:19:31 +0100
From: Matthias Paul <PAUL-MA AT reze-1 DOT rz DOT rwth-aachen DOT de>
Subject: Re: QEMM and DR-DOS
To: opendos AT delorie DOT com
Reply-to: Matthias DOT Paul AT post DOT rwth-aachen DOT de
Message-id: <368037F2F@reze-1.rz.rwth-aachen.de>
Organization: Rechenzentrum RWTH Aachen
Precedence: bulk

On Sat, 16 May 1998 Dean Dancey wrote:
> [...]
> I am getting much better performance, but on an itial boot I am 
> getting two error messages which are waaayyy out of my area of 
> knowledge: 
> Could not find ROM handler for INT 1A
> DOS-UP ERROR: DOS SUB-SEGMENT LIST UNMOVEABLE

Well, these two messages are displayed because of some recent 
and necessary changes in the DR-DOS kernel (since DR-OpenDOS 7.02+). 

The first message is displayed because of DR-DOS  Year 2000 support 
which intercepts INT 1Ah. Unfortunately, QEMM is making some (IMHO 
invalid) assumptions, hence you have to insert the following line in
CONFIG.SYS prior to loading the QEMM memory manager:

 YEAR2000=off

This will disable the internal Year 2000 handler and you will need 
a ROM-BIOS and RTC chip supporting the Year 2000 instead.
 
The second message is displayed because QEMM makes some assumptions
on the memory layout of the DOS data structures, which have been
valid until including OpenDOS 7.01. However, DR-OpenDOS 7.02 now
comes with its own FILESHIGH= and FCBSHIGH= features, which 
initally was able to load all but 5 Handles in UMBs. However, due to
some bugs in Windows and Windows for Workgroups 3.xx, which 
expect at least 8 Handles to be in low memory, the default setting
has been changed to have at least 8 Handles low. If you have a look
at the 

 INSTALL=c:\opendos\mem.exe /AP 

output during CONFIG.SYS under OpenDOS 7.01, you ll see, that there
are only 5 Handles available at this time. If you run MEM in
AUTOEXEC.BAT or later, you ll see that the amount of Handles has
changed to the value x (<= 255) given by FILES+FCBS. The Handles are 
organized in two chunks, the first always has 5 Handles, the second 
holds the rest (a minimum of 3, since the minimum of Handles for the 
running system is 8 to be compatible with MS-DOS).

Now, with DR-OpenDOS 7.02+, Handles can be loaded high, but 8 Handles
still have to stay low for compatibility with Windows. Hence the
memory layout during CONFIG.SYS is 5+3 Handles, which will always stay
low, while additional Handles can be loaded high in a third chunk.

This minor change is what upsets QEMM and it would be almost trivial
to change QEMM just to accept this memory layout (since by definition,
Handles must not necessarily be held in 2 chunks). However, this
change is up to Quarterdeck, not to Caldera.

However, some late issues of Windows don t have these problems with
less than 8 Handles in low memory, so there is a chance to use
QEMM on DR-DOS and still running such a version of Windows without
problems, if the default minimum value of Handles is set back to 
5 instead of 8. If you have the IBMBIO.COM source (as I have learnt 
in the meantime, only available on CD-ROM), it s easy to change this 
setting. Maybe this could be made configurable in IBMBIO.COM, which 
is not that easy, since this 5 or 5+3 layout is already established 
before CONFIG.SYS is processed.

Some months ago, I have written an automated patch for this problem,
and I may post it here in a few days, so that all people who prefer
using QEMM over using Windows (or have a very late issue of Windows 
3.1x installed) can take advantage of both.

 Matthias
 
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 eMail: <Matthias DOT Paul AT post DOT rwth-aachen DOT de>
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