Writing DMK back to floppy

Prophet (3954)

26-06-2022, 06:55

I thought for a long time writing back a DMK file back to floppy was not possible. I recently received a Fujitsu FM77AV and whilst images exist, getting them on disk was not straightforward. The images are in Pasopeia D88 format, have 40 tracks, 16 sectors per track and 256 bytes per sector. The format originated on 5.25” floppy drives in Japan but was later also used on 3.5” floppy drives (to ensure compatibility with existing software I assume). The double step the head to simulate 40 tracks (leaving every other track unused).

Well all that is not so relevant to MSX but it lead me to search for a way to write the images to disk. Through some miracle (whilst looking for PC-8801 info as it also uses this format) I found SAMdisk which proved to be able to write these images to floppy! Then I looked a bit further and it supports DMK format as well… here is a list of all the formats it supports.

I have yet to try it out but certainly will soon.

Por wouter_

Hero (522)

26-06-2022, 09:37

sdsnatcher73 wrote:

I thought for a long time writing back a DMK file back to floppy was not possible ...

DMK is a fairly generic disk image format, it can represent a wide variety of disks. It can represent many (most) copy protections, but also regularly formatted disks. And obviously the latter can be written back to floppy

Another important factor is the machine/device you're using to write the floppy. E.g. on MSX, disk drives controlled via a WD2793 FDC (or clone) are able to write a different subset of all possible DMK files than disk drives controlled via a TC8566AF. SAMdisk (on PC?) will be able to write another subset.

As a first approximation: on MSX with a WD2793 FDC, it should be possible(*) to write all DMK files, as long as there are no overlapping sectors and all sector numbers are below 0xF5.
(*)"Possible" as in "technically possible", I don't know of any generic tools that allow you to do this.

Although this article is not about copy protections, it does contain some background information and hints about what the possibilities/difficulties are with writing arbitrary disk formats (section 4.3 formatting a track).

Por sdsnatcher73

Prophet (3954)

27-06-2022, 15:26

Of course I meant that there are no tools available to do it

Por jepmsx

Master (253)

13-07-2022, 12:11

Hi sdsnatcher73!

I'm trying to recover some floppy disks using samdisk, but when I try samdisk a: nameImage.dsk it detects the floppy as 83 tracks in place of 80. I've tried to fix the size using -c80 but then it doesn't change the heads, it only reads 1 or 0, not both.

Is there a way to fix the geometry for samdisk tool?

Por sdsnatcher73

Prophet (3954)

13-07-2022, 13:45

I have used it only for writing images. But in my experience it will default to 84 tracks (0-83) but will “record” the last 4 tracks as unformatted (that is what I saw when writing many images).

Por jepmsx

Master (253)

13-07-2022, 18:49

Thanks for the information

Por tingis53

Paragon (1119)

13-07-2022, 21:57

Hi
I've been readind this thread for several days and I don't know if this can hel you
I got original copies of several disks From a DMK copy using a program called PDT.exe to convert it to the PDI format and then with DSK-PRO I got perfect copies of the originals including the protrections .
I don't know as well if it works for 100% of the DMK copies but for me it worked,

Por sdsnatcher73

Prophet (3954)

13-07-2022, 23:26

Do you have a link to this tool?

Por tingis53

Paragon (1119)

14-07-2022, 08:49

well it's easy I just tried yesterday an it worked , just google PDT.exe and the link appears , Its a PC tool in command line

Por tingis53

Paragon (1119)

14-07-2022, 08:54

Sory I made a mistake what you have to look for is DMK to PDI