Dual format ST+Amiga floppies write

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AdamK
Posts: 8
Joined: Sun Oct 14, 2018 7:45 pm

Dual format ST+Amiga floppies write

Post by AdamK »

I'm looking if it is possible to create (from perfect digital image) and write dual format (ST+Amiga) floppy images using Kryoflux. Has anybody know how to attempt that?
brightcaster
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Joined: Fri Nov 08, 2013 10:48 pm

Re: Dual format ST+Amiga floppies write

Post by brightcaster »

What format/container is your "perfect digital image"? As there are different approaches to dual booting capability it would be a good starting point to know that at least...

David
AdamK
Posts: 8
Joined: Sun Oct 14, 2018 7:45 pm

Re: Dual format ST+Amiga floppies write

Post by AdamK »

I'd like to autor the disk: combine ADF and ST images into one image (kryoflux stream?) and write it to floppy so it would be readable both on ST and Amiga.
If there are better ways to do that, I'm open to suggestions.
brightcaster
Posts: 453
Joined: Fri Nov 08, 2013 10:48 pm

Re: Dual format ST+Amiga floppies write

Post by brightcaster »

Ahh, that's a different thing! Your first postings reads to me as if you already have a working image of a dual floppy (I also wondered what format that image could be other than ipf) which you like to write back to a physical floppy...

I guess that there are different approaches to create a dual boot floppy. I remember some kind of magazine floppy (back in the 80s or early 90s) which had a bootblock for both (amiga and PC in that case) on track 0. The rest was in a custom format so that the data (some kind of magazine) could be shared by booth systems.

So there haven't been any directories or filesystems on that floppy. If you inserted them in the running machine (not booting from them) they couldn't be accessed as normal floppies (NDOS on the amiga and read error on the PC).

So it will be almost impossible to get the two floppies you have (which I assume, need a working filesystem to access there files) onto one dual boot floppy!

David
ZrX
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Joined: Tue Dec 06, 2011 9:09 pm

Re: Dual format ST+Amiga floppies write

Post by ZrX »

Creating those dual format disks is somewhat complicated and you can't really share data between two different filesystems on a "DOS" disk.

The important thing is to know that Atari (and PC) have the filesystem descriptors at the first tracks while Amiga has them mostly at the midway of the disk. But Amiga also requires the boot data on the first track.

So you need to map the diskspace accordingly to each system such that each system is seen as already allocated or unavailable space to the other.

With the Amiga boot track you have to mix two different sector formats on the first track so each system only sees what they need for everything to work.

All in all, if you can setup each filesystem accordingly and build suitable tool for generating the first track as KryoFlux raw stream you could write back such a disk.
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mr.vince
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Re: Dual format ST+Amiga floppies write

Post by mr.vince »

I have several IPFs that'll write and work fine, so called Amiga-ST dual boot disks (if I remember these are Thalion games). So in a nutshell... yes, this works and it's not something special if we're looking at this from the encoding perspective. The "magic" is how to lay out and format the data so the disk will in fact work in e.g. PC, Atari and Amiga.
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