Mail Archives: opendos/1999/04/19/06:54:12
On Fri, 16 Apr 1999 Dan de Haan wrote:
>> DR-OpenDOS 7.02 and DR-DOS 7.02 had a provision to actually boot
>> out of other physical hard disks than 80h (if you had a modified
>> MBR and Boot Sector, that preserved the DL register value), but
>> this has been backed out for some compatibility issue on systems
>> with strange partitioning schemes. [...]
> I could just use v. 7.02, if I were too, how would I make it boot
> off of the second Hard drive (drive d:) Would I need a boot manager
> program, if so which would work best.
Don't know, I was using LOADER in conjunction with BOOTLOAD, but
others may be better.
By default the boot sector written by DR-DOS 7.02+ SYS will preserve
the DL register content, which holds the physical boot drive unit
(00h, 01h for floppies A: and B:, and 80h, 81h, 82h, 83h for
harddisks) similar to MS-DOS boot sectors. Older DR DOS boot sectors
always had a fixed drive unit patched in. For compatibility reasons
with very old & odd ROM-BIOSes you can still force SYS to write such
an 'old style' boot sector using its new /O option, however, you can
now also override the unit /O:nnn. The DR-DOS 7.02 IBMBIO.COM will
take DL into account when searching for IBMDOS.COM, [D]CONFIG.SYS,
etc. and that's what you'd need when actually booting off other
physical drives without swapping drives.
For floppy media, the DL value is usually set by the ROM-BIOS, when
it gives control to the boot sector, so you'd already have all you'd
need to boot off floppy B:. For harddisks, the ROM-BIOS will pass
DL to the Master Boot Record instead of passing it to the Boot Sector.
Hence it depends on the Master Boot Record, if it too preserves the
DL value before launching the Boot Sector. The DR-DOS 7.02+ MBR
(FDISK) is prepared to do so, but this has not yet become enabled.
Though LOADER does not support this officially, many other boot
managers do have means to select the drive unit. If you can't find
a better tool you could use for example my BOOTLOAD 1.0 utility
(a LOADER auxilliary which still in BETA) to boot of other physical
drives. It was meant to be put on my web site, but since I haven't
found the time to update for a long while now, you'd still have to
ask me privately for a copy. But it won't work with DR-DOS 7.02
updates and DR-DOS 7.03, even if you'd have a boot manager
that directly loads IBMBIO.COM of other physical drives.
I still hope, it won't last forever until a 100% solution will be
implemented into DR-DOS...
Matthias
-------------------------------------------------------------------
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
-------------------------------------------------------------------
- Raw text -