DOS ain't dead

nico7550 10.07.2025, 09:04	Bootsector and DMF disk (Users) Post reply
	Hi, Can you explain to me why a DMF floppy disk freeze at boot when the same disk but in 1.44Mb format (the DMF file converted using WinImage) works? I have the problem with older DOS but not with more recent ones so I assume it's a problem of unsupported format in the kernel files? Thanks Upload of my test images: `megawrzuta.pl/mmctkfxc`

roytam 11.07.2025, 07:45 @ nico7550	Bootsector and DMF disk Post reply
	as DMF has more sectors per track (normal: 18, DMF: 21), kernel may not know part of itself is in "extra" sectors of same track.

nico7550 12.07.2025, 08:21 @ roytam	Bootsector and DMF disk Post reply
	> as DMF has more sectors per track (normal: 18, DMF: 21), kernel may not > know part of itself is in "extra" sectors of same track. Thanks, so there nothing that can be done...(?)

roytam 12.07.2025, 11:50 @ nico7550	Bootsector and DMF disk Post reply
	> > as DMF has more sectors per track (normal: 18, DMF: 21), kernel may not > > know part of itself is in "extra" sectors of same track. > > Thanks, so there nothing that can be done...(?) For FreeDOS, maybe you can modify its boot sector source and FreeDOS boot related source to handle BPB and DMF disk?

fritz.mueller Munich, Germany, 12.07.2025, 11:52 @ nico7550	Bootsector and DMF disk Post reply
	https://archive.org/details/vgacp625 vgacopy says that it supports DMF (Win98), I already tested it with FreeDOS and 3,5 inch diskettes, worked fine, but I do not know if the older 5,25 diskettes are supported too.

nico7550

12.07.2025, 23:04

@ fritz.mueller

Bootsector and DMF disk

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Even if we slightly switch of subject, thanks.

1. The maybe only impossible solution will be to have 2 types of track size, 18 sectors for around 250-300Kb and 21 sectors for the rest of the disk, or someking of dual partitions?

2. Can someone test 2M please, I try on 86BOX and QEMU, I still got density error when I try to format using MS-DOS format or 2MF? (https://www.youtube.com/watch?v=venQZPVeCNs / http://www.win3x.org/win3board/viewtopic.php?t=25019&view=min). Even using VGACOPY and selecting the 2M size didn't works...

roytam

13.07.2025, 05:55

@ nico7550

Bootsector and DMF disk

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> Even if we slightly switch of subject, thanks.
>
> 1. The maybe only impossible solution will be to have 2 types of track
> size, 18 sectors for around 250-300Kb and 21 sectors for the rest of the
> disk, or someking of dual partitions?
>
> 2. Can someone test 2M please, I try on 86BOX and QEMU, I still got density
> error when I try to format using MS-DOS format or 2MF?
> (https://www.youtube.com/watch?v=venQZPVeCNs
> /
> http://www.win3x.org/win3board/viewtopic.php?t=25019&view=min).
> Even using VGACOPY and selecting the 2M size didn't works...

emulators don't support custom size of floppy well.

marcov 25.07.2025, 23:10 @ nico7550	Bootsector and DMF disk Post reply
	> Can you explain to me why a DMF floppy disk freeze at boot when the same > disk but in 1.44Mb format (the DMF file converted using WinImage) > works? Hardcoded values in the bootsector/and or a bios call there that doesn't support DMF ?

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