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[Info-mtools] mtools version 4.0.18 do not recognise old DOS floppies (i
From: |
Jörg Jenderek |
Subject: |
[Info-mtools] mtools version 4.0.18 do not recognise old DOS floppies (invalid BPB) |
Date: |
Tue, 18 Jun 2013 17:08:32 +0200 |
User-agent: |
KMail/1.9.6 (enterprise 20070904.708012) |
Hello,
i tried to handle some old DOS floppies. They are not recognised by mtools
version 4.0.18. The images work well inside the DOS emulator.
After some experiments with using dd to replace the boot sector and a hex-
editor, i realised that the appended FATs, the root directory and the data
area are valid. But the boot sector does not contain a valid BIOS parameter
block (BPB) especially no usable media descriptor.
Afterward i found the explanation at
http://en.wikipedia.org/wiki/File_Allocation_Table#Exceptions
So when you take the media descriptor inside the FAT, look for the
corresponding floppy values, all examples of old DOS floppies can be
accessed by this information.
So it would be nice if newer mtools version can use this flow of logic to
access floppy medias.
All sample image files for further examinations are stored under
http://mitglied.multimania.de/jenderek/mtools/
regards
Jörg
--
Jörg Jenderek email: joerg.jen.der.ek (at) gmx.net
Germany PGP: B9FE A356 283E 0048 6389 18BF AFF2 B1C9 421A D4D6
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