Date:	Thu, 03 Jul 1997 15:32:37 +0100
From:	Matthias Paul <PAUL-MA AT reze-1 DOT rz DOT rwth-aachen DOT de>
Subject:	Re: Win95 and OpenDOS: an experiement.
To:	opendos AT delorie DOT com
Reply-to:	Matthias DOT Paul AT post DOT rwth-aachen DOT de
Message-id:	<1971BD508C4@reze-1.rz.rwth-aachen.de>
Organization:	Rechenzentrum RWTH Aachen

Hi.

While updating and enhancing COD's IBMBIO.COM, I also tried to make
it a bit more compatible with MS Windows95.  Though we have 
e.g. LOADER (checked this with a version from DR/Novell and with 
CCI's version from Multiuser DOS) running Novell DOS, OpenDOS, and 
Windows95/MS-DOS/PC-DOS piecefully together on the same hard disk 
partition (using the undocumented SYS /DR:ext), I thought it was 
great, if we could force Windows95 start menu to load OpenDOS via 
the "'old' DOS version" item, where it normally complains about 
"wrong version of MS-DOS".

I tracked this problem down to Windows peeking a few bytes in 
IBMBIO.COM to retrieve it's version.  After patching our IBMBIO.COM 
to have the same magic numbers at the same places, Windows actually
lauched our IBMBIO.COM.  Unfortunately, our IBMBIO.COM crashed soon
after this.  I'm sure this is manageable, since - at this moment - 
we don't need any Windows code any more (Windows has just played being
a 'boot sector').  However, there must be some difference (register
values, loading position of the code, etc.) compared to our own
boot sector code.  To avoid length debugging sessions, does anybody 
having ad-hoc knowlegde of these details?  

BTW, does anybody know the details on the differences between 
DRVSPACE from MS-DOS 7 and DRVSPACE from MS-DOS 6.22 (internal 
version numbers etc.).  My updated IBMBIO.COM now also works with 
DRVSPACE from MS-DOS 6.22, but refuses to load DRVSPACE from MS-DOS 
7, although MS-DOS 6.22 does load MS-DOS 7' DRVSPACE... Any DRVSPACE 
expert having in-deep knowlegde in this area?

 Matthias
 
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