DSK file format description

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Dbug
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DSK file format description

Post by Dbug » Thu Feb 02, 2006 12:59 pm

I was trying to figure out how to patch DSK files, and then I checked the Tap2Dsk tool that seem to work with a simple format:
- a 'imageheader' of 256 bytes, followed by 'n' sectors of 256 bytes.

With this I would just have to put the Jasmin boot in DSK+256, the MicrodiscBoot at DSK+512, and the fake directory at DSK+768.

Unfortunately, I just checked on one my DSK, it does not seem quite right, it seems that if the disc title is MFMDISC, then there are additional synchro stuff between sectors, in the following format:

Code: Select all

F7 F7 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E
4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 4E
4E 4E 4E 4E 4E 4E 4E 4E 4E 4E 00 00 00 00 00
00 00 00 00 00 A1 A1 A1 FE 29 01 10 01 F7 F7
etc... with some numbers changing depending of which track/sector it is on.

Have you the exact format described somewhere, and how to detect the various variants, or at least just the general formula I can use to locate in the file a particular sector/track ?

Thanks :)

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Symoon
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Post by Symoon » Fri Feb 03, 2006 12:54 am

Hi there,

A while ago, I think it was in 2003, the CEO Mag published an article describing the .DSK files header, as well as articles about OLD2MFM, and so on.
See: - CEO Mag 154, page 49
- CEO Mag 153, page 16
- Sedoric à Nu gives all details about the disk formats and the gaps: http://oric.free.fr/DISKS/sedna3_0.pdf
http://oric.free.fr/DISKS/sednb3_0.pdf
http://oric.free.fr/DISKS/sednc3_0.pdf

You can also check the sources from Fabrice's tools.
I was about to try and find how I was doing in Oric Disk Manager, but the source is somewhere on another computer, it's too late for today.

Anyway, an MFM disk, IIRC, is based on a 256 bytes header, and then the whole disk, physically, including its gaps between the sectors, and so on.
The "old" Euphoric DSK format (the one you convert with OLD2MFM) also had a 256 bytes header, with "ORICDISC" or something similar, but only included logical datas from the disk (the sectors). Not the gaps.
Fabrice will correct me if I'm wrong.

Hope this helps
Simon

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Euphoric
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Post by Euphoric » Fri Feb 03, 2006 11:01 am

Fabrice will correct me if I'm wrong.
That's perfectly correct.

Simon said. :wink:

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Twilighte
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Post by Twilighte » Sat Apr 05, 2008 5:18 pm

ok 2 or 3 years later and i am finally on the disk trail. However me being me i still don't speak French (with More french friends than English ones you would have thought i'd have learnt some by now?).
I looked at sedoric a nu but could not see any description of boot stuff.
I remember donkey's years ago it being mentioned that all oric's look for bootup.com in track 0 of the inserted disk on bootup and that sedoric has this but redirects everything after to boot its own system.
However i am still none the wiser in knowing how all this works (in English).
If someone could provide me with a little English guide to how Disks boot on Oric, then i would be very happy, otherwise i will continue to search the net for the answers.

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waskol
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Post by waskol » Sat Apr 05, 2008 6:55 pm

Twilighte wrote:ok 2 or 3 years later and i am finally on the disk trail. However me being me i still don't speak French (with More french friends than English ones you would have thought i'd have learnt some by now?).
I looked at sedoric a nu but could not see any description of boot stuff.
I remember donkey's years ago it being mentioned that all oric's look for bootup.com in track 0 of the inserted disk on bootup and that sedoric has this but redirects everything after to boot its own system.
However i am still none the wiser in knowing how all this works (in English).
If someone could provide me with a little English guide to how Disks boot on Oric, then i would be very happy, otherwise i will continue to search the net for the answers.
All the boot stuff for microdisc and Jasmin are very well described in various issues of theoric (well the mag was in French my unlucky friend).
Anyway, if you wan't to dig out some stuff, you can find Micr'oric and Theoric here :
Theoric : http://abandonware-magazines.org/affiche_mag.php?mag=56
Microric : http://abandonware-magazines.org/affiche_mag.php?mag=57

Otherelse, an issue of the ceo mag, freely downlable has an Euphoric DSK and .TAP file description :
http://andre.cheramy.net/telechargement/ceomag-url.pdf

OK, for now, it is not in english, but it is a start.

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