Need advice on how to recover 5.25" floppy

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brightcaster
Posts: 224
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need advice on how to recover 5.25" floppy

Post by brightcaster » Wed Oct 30, 2019 6:34 pm

You have to adjust the "Track Distance" switch in the image profil settings. You are using a 40 track device but the kryflux is double stepping the tracks as if it is conected to a 80 track drive. That's why the orange T boxes apear indicating that the track number is not corresponding to what's expected. For example if the head moves from track 0 to what is expected to be track 1 it reads track 2 because doublestepping is configured. That is indicated by the orange T box.

So if you use the menu of the gui go to files/settings, choose the current image profile (for example CBM DOS sector image) and set the "track distance" field to "40 Tracks".

David

harlus
Posts: 29
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Thu Oct 31, 2019 8:38 am

Thanks for your fast reply.
I adjusted the setting as you suggested (40 tracks instead of 80), but unfortunately nothing changes, i get a situation identical to the previous screenshots i posted (doublestepping and "T" orange boxes).

harlus
Posts: 29
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Mon Nov 04, 2019 10:19 am

Here is the preservation stream, maybe it's useful to understand my problem:

https://filebin.net/hpdgc0zcj3kvdsrg

brightcaster
Posts: 224
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need advice on how to recover 5.25" floppy

Post by brightcaster » Mon Nov 04, 2019 1:30 pm

Beside the 40/80 track issue the disk is very noisy from the start off but gets even more worse towards the inner tracks! That corresponds with the fact that the inner tracks are written with lower speed on a c1541 resulting in shorter fluxchanges when reading with todays drives using constant speed.

Unless the disks surface and the heads where cleaned properly before reading I guess this disk is fading away. I'ts not the usually problem with some mold spots ore similiar which only effects partial areas of the surface. This floppy is in a very bad condition as a whole...

On the other hand it could also be a drive related problem as there are some dd drives which don't like GCR coding at all. I prefer the hd panasonic ju-475 for reading c64 stuff!

David

ZrX
Posts: 578
Joined: Tue Dec 06, 2011 9:09 pm

Re: Need advice on how to recover 5.25" floppy

Post by ZrX » Mon Nov 04, 2019 5:38 pm

Either the disk is just bad or the drive that was used to write the disk is out of alignment.

The drive dumping the disk has no problem with 1541s GCR-coding, the scatter plot shows the drive filter cuts off way below the fastest bitcells when looking at the noise from the unformatted tracks.

The stepping issue is that as KryoFlux was designed to be used with 80-track drives it can't be configured to manage disks with a 40-track drive. To do any track analysis with a dump generated using a 40-track drive the user has to manually rename the files for correct track numbers.

brightcaster
Posts: 224
Joined: Fri Nov 08, 2013 10:48 pm

Re: Need advice on how to recover 5.25" floppy

Post by brightcaster » Mon Nov 04, 2019 7:52 pm

Whow, I just learned something new again! I always used the track distance parameter -k to read mfm 40 track dd disks. But I never recognized that this feature is not available for the gcr coded formats! I understand that the decision was made to avoid problems with fat/half-tracks etc...

But wouldn't it be nice to read dd disks with a 48tpi drive (only true cbm format floppies with no copy protection involved)? Because the gap in the had is a bit wider (compared to a 96 tpi drive) it should result in a better signal/noise ratio (assuming that disk was written with a 48 tpi head, but hey the 1541 had a 48tpi head afaik)!

Or am I missing something and have to learn more again today ;-)

David

ZrX
Posts: 578
Joined: Tue Dec 06, 2011 9:09 pm

Re: Need advice on how to recover 5.25" floppy

Post by ZrX » Mon Nov 04, 2019 10:54 pm

I think I have a couple of DD drives. Should measure if there's any significant difference in the head signal between DD and HD drives when reading 1541 floppies.

harlus
Posts: 29
Joined: Wed Jan 16, 2019 7:06 pm

Re: Need advice on how to recover 5.25" floppy

Post by harlus » Tue Nov 05, 2019 10:08 am

Probably these disks are just bad, they were written many years ago, i think around 1985.
However, while i'm at it, i'd like to take a dump of these disks, even if there will be many demaged sectors.

So, if I uderstood correctly, the procedure to do this is:
1) take a preservation stream of the disk
2) rename the tracks
3) use the preservation stream as input file, and obtain a .d64 or .img file

For me it's not clear how to do 2) and 3).

For point 2): How do i rename the files? It would be fast to do with a .bat file, but i need to know how to rename them, can you tell me as an example how to rename these files?
track00.0.raw --> [new name]
track00.1.raw --> [new name]
track01.0.raw --> [new name]
track01.1.raw --> [new name]
track02.0.raw --> [new name]
track02.1.raw --> [new name]


For point 3): can you tell me the syntax to do this? I imagine that it's not possible from the GUI.

ZrX
Posts: 578
Joined: Tue Dec 06, 2011 9:09 pm

Re: Need advice on how to recover 5.25" floppy

Post by ZrX » Tue Nov 05, 2019 10:45 am

You'd need to space the tracks from 40 to 80.

track00.0.raw -> 00.0.raw
track01.0.raw -> 02.0.raw
track02.0.raw -> 04.0.raw
track03.0.raw -> 06.0.raw
track04.0.raw -> 08.0.raw
...

For side 1 tracks you'd have to start from track 8 (track00.1.raw -> 08.1.raw) and you'll lose the first four tracks as reading those requires the flippy modified drive.

Renaming could be done from a commandline with some batch script. There are also software like Total Commander that has a multi rename -feature where you select all the *.0.raw files, then set a destination filename+counter+.0.raw that counts from 0 in steps of two in two digit accuracy.

SomeGuy
Posts: 243
Joined: Wed Feb 18, 2015 8:18 pm

Re: Need advice on how to recover 5.25" floppy

Post by SomeGuy » Tue Nov 05, 2019 12:04 pm

Most "360k" floppy drives have issues reading GCR encoding. Your best bet at reading them is probably a "1.2mb" Teac drive.

Of course, it is difficult to reliably write 48tpi (360k) images in a 96tpi (1.2mb) drive and KF does not support writing non-index aligned streams. But for reading and archiving, it is fine.

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