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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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