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Book8088's CF2IDE stumps Freedos boot (Users)

posted by boeckmann, Aachen, Germany, 30.01.2024, 19:21

> > > Than I just return a backup to the CF card with "dd". Something like:
> >
> > @bocke may you upload the MS-DOS image so that I can examine it?
> >
> > You can upload the file directly to
> > https://nextcloud.iww.rwth-aachen.de/index.php/s/rjmZzcJrZkWMcrE
>
> I uploaded it right now. I checked it and this image works when copied to
> CF via "dd". It boots.
Thanks for providing this. The BPB of the partition shows some interesting things I did not see until now:

Partition table entry:
80 01 01 00 06 FE 3F 3D 3F 00 00 00 7F 32 0F 00

Volume boot record:
EB 58 90 20 20 20 20 20 20 20 20 00 02 10 01 00
02 00 02 00 00 F8 F8 00 00 00 00 00 00 00 00 00
00 79 0F 00 00 00 29 00 00 00 00 20 20 20 20 20
20 20 20 20 20 20 46 41 54 31 36 20 20 20 00 00
...

Offset 0x18 and 0x1A of the volume boot record, which should specify the sectors per track and head count, are zero. The partition table entry confirms that the partitions were indeed created under the assumption that the head count is 255. I did not see this either for such a small partition.

Would be interesting to see what INT13,08 (and 48, for completeness) actually return as geometry. Does anyone know a tool which simply dumps these values?

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