Mail Archives: opendos/1998/06/12/12:29:51
On Thu, 11 Jun 1998 Charles Dye wrote:
> Nothing new there! That was true in Windows 95 for any version of DR DOS --
> Caldera's, Novell's, DRI's. The Win95 boot loader looks for a version
> signature at the start of IO.SYS / IBMBIO.COM which exists in all releases
> of MS- and IBM DOS, but not in DR DOS.
Correct. You can find some details in the (now outdated) IBMBIOA3.ZIP
archive still downloadble from my web pages (README.TXT and BOOT.TXT).
> after a merry afternoon disassembling and patching Microsoft's signature
> check, dual-boot *still* wouldn't work with DR DOS. There's some difference
> in the way the boot files are loaded that I haven't been able to figure out.
MS-DOS boot sector (and the Windows 95 dual boot loader, which just
emulates a boot sector) only loads the first 512 bytes of the IO.SYS
(alias IBMBIO.COM) file into memory, which in MS-DOS contains a loader
stub to load the rest of the file - hence all these MS-DOS position
dependencies of the IO.SYS file on the disk - something completely
unknown by DR-DOS right from the start.) As the DR-DOS boot sector
loads the whole BIOS file into memory, there is no need for such a
loader stub in DR-DOS IBMBIO.COM. However, if you load DR-DOS
IBMBIO.COM using Windows 95 dual-boot (this is possible using for
example my experimental FIXUPBIO utility), IBMBIO.COM will immediately
jump into memory not initialized by the Windows 95 boot loader, and
therefore will crash.
Microsoft has started to fade out their dual boot loader with their
introduction of FAT32 in OSR 2. So you cannot even reliable dual boot
MS-DOS 6.22 and MS-DOS 7.10 for example.
Using DR-DOS LOADER is much more flexible anyway, as it supports
many other operating systems, too. However, because of the position
dependencies of the MS-DOS kernel files on disk, LOADER supports
only one out of the MS-DOS OSes at a time (the last one SYSed).
Obviously that s not Caldera s fault...
Matthias
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Matthias Paul, Ubierstrasse 28, D-50321 Bruehl, GERMANY
eMail: <Matthias DOT Paul AT post DOT rwth-aachen DOT de>
Web : http://www.rhrz.uni-bonn.de/~uzs180/mpdokeng.html
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