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List of known Disk ][ protection schemes
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vladitx



Inscrit le: 19 Déc 2007
Messages: 22

MessagePosté le: Sam 29 Déc 2007, 20:38    Sujet du message: List of known Disk ][ protection schemes Répondre en citant

I don't know if this has already been done, but I need to gather information about used protection methods for upcoming imaging/emulation. Most of the information was provided by Toinet, but Deckard added as well. With every new piece of information I would be able to edit this post in an attempt to keep things sorted.

Known techniques

(0) Write-protection notch:
Simply requiring the diskette to be write protected.

(1) Prologue/epilogue change:
Substitution of standard RWTS address/data field prologues/epilogues (D5AA96/DEAAEB, D5AAAD/DEAAEB) with something else.

(2) Address field change:
Providing "incorrect" data in address field, e.g. wrong track number.

(3) Sector layout change:
Using non-standard sector size/count/layout, including different than 6+2 encoding.

(4) Nibble translation change:
Substitution of standard RWTS nibble table with something else.

(5) Nibble check:
Checking for certain nibbles, their timing in cycles (32, 36, 40, etc) and/or their count on a track. Nibble values may be used indirectly to decode further data.

(6) Non-standard tracks:
Placement of data on half/quarter tracks and/or track numbers higher than 34, in contrast to standard RWTS using only whole tracks (0 .. 34).

(7) Synchronized tracks:
Writing data on tracks in a special relation allowing to find certain data on different track(s) at precise moments in time (angular position).

(8) Partial tracks (spiralling):
Splitting data between tracks such as after reading part of one track and moving the head the stream will continue on some other track.

(9) Weak bits:
Leaving parts of medium weakly or un-magnetized such to allow formation of random transitions in the pulse shaper.

(10) Holes:
Damaging medium in specific positions such as certain sector's data, rendering runtime write attempts fail.
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vladitx



Inscrit le: 19 Déc 2007
Messages: 22

MessagePosté le: Mar 08 Jan 2008, 1:39    Sujet du message: Répondre en citant

I forgot to state that I welcome all corrections/additions.

There is a question: part #8, "Partial tracks (spiralling)". Does anybody know whether it continues to read stream during head movement or it stops during that period? On one hand, head movement (load) times will vary wildly between drives, but on the other the head is wide enough to compensate probably for the movement tolerance.

So, anyone with more precise description of this technique and/or example titles using it? This is my murkiest part so far ...
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.



Inscrit le: 29 Mar 2007
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MessagePosté le: Mer 09 Jan 2008, 0:48    Sujet du message: Répondre en citant

vladitx a écrit:
So, anyone with ... example titles using it?


Have a look to early Electronic Arts softwares such as Skyfox or Archon.

JM
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JPL
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Inscrit le: 12 Mar 2007
Messages: 165
Localisation: Issy les Moulineaux / PARIS

MessagePosté le: Lun 14 Jan 2008, 12:53    Sujet du message: Répondre en citant

You can see a track arcing here
http://www.hackzapple.com/DISKII/ARCING/ARCING.HTM

A DSL connexion is nice Wink
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JPL
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MessagePosté le: Lun 14 Jan 2008, 12:57    Sujet du message: Répondre en citant

A classification is here (in french sorry Embarassed )
http://www.hackzapple.com/ORG1/MZ/PIRATESOFTS1.HTM

Never easy to do that but your system is nice too.
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JPL
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MessagePosté le: Lun 14 Jan 2008, 12:59    Sujet du message: Répondre en citant

Weak bits : I never encountered this system on Apple II but only on IBM PC. Impossible to do a copy of course (as Prolok) but easy to remove.
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vladitx



Inscrit le: 19 Déc 2007
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MessagePosté le: Mar 15 Jan 2008, 14:02    Sujet du message: Répondre en citant

Thanks, guys. Would somebody be so kind as to translate the two paragraphs in English?

Citation:
LE SPIRALING

Ce n'est pas à proprement parler une belle spirale qui partirait d'un bout de la disquette et qui irait vers le centre mais plus exactement des enregistrement de quelques secteurs (mais en général on a affaire à un seul secteur de plusieurs pages) sur des demi-pistes contigues. La copie s'avère délicate du fait de la diaphonie.

LE "TRACK ARCING

Favori d'ECA il s'agit d'une forme de spiraling sur 2 ou 3 pistes mais en faisant un aller et retour. Lors du test de ce track arcing le bras du drive fait un bruitage très spécifique. Pour l'entendre (et peut être le voir si vous avez une ligne de connexion ADSL) examinons celui de SKYFOX ... grâce au prêt par mon ami Antoine de son super appareil photo numérique ! Mille Mercis Antoine.


I as I see from the video the head does track stepping back and forth around a given track, but my question still remains - is the stream continuous or not? If the software stops reading while head is moved it's still okay for imaging, but if the stream continues during the head movement process (in a quite bizarre curve) ... well, it becomes a little nightmare.
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.



Inscrit le: 29 Mar 2007
Messages: 350

MessagePosté le: Mar 15 Jan 2008, 14:57    Sujet du message: Répondre en citant

vladitx a écrit:
If the software stops reading while head is moved


In "move arm" routine, afaik, there's always a timing routine (based on theorical hardware delay).
No read are done: software just waits in a "cycles counted" loop (new routine or JSR to a known routine in ROM).
After that delay, the arm should be on the right track and the program begins to read new nibbles.

JM
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vladitx



Inscrit le: 19 Déc 2007
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MessagePosté le: Mar 15 Jan 2008, 16:24    Sujet du message: Répondre en citant

Deckard, are you sure this is the case for track Spiralling/Arcing? My question is only about it.

I can imagine that with the sufficiently wide head one can magnetize the stepper coils quarter-track inward/outward and still continue to be in "bounds" to receive the stream without interruption.

Toinet, do you happen to have dissected Skyfox code?
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JPL
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MessagePosté le: Mar 15 Jan 2008, 17:07    Sujet du message: Répondre en citant

SPIRALING
That's not a real spiral form one side to and other in continum as the old music disks but a record of two, three ord four pages (ie sectors) on half track. (nota : you can do on quarter tracks of cause but on half track it's enough to have a disk very difficult to copy)

TRACK ARCING
Favorite form ECA , you wrote the same things as SPIRALING on 2 or 3 tracks but you come back : for this reason it's more hardly to copy

Suppose you cas see transform the circle of a track into a line

In DOS 33 you'll see the sectors XX as is :

Track X,0 __XX__XX__XX__XX__XX__XX__XX__XX __XX__XX__XX__XX__XX__XX__XX__XX
Track X,5 ________________________________________________________________
Track Y,0 __XX__XX__XX__XX__XX__XX__XX__XX __XX__XX__XX__XX__XX__XX__XX__XX
Track Y,5 ________________________________________________________________
(ok for explications I've draw as if synchronisation between the two tracks exist but in reality it's never do or if it's, that's an accident)


With SPIRALING You'll see

Track X,0 __XXXXXX________________________________________________________
Track X,5 _________________XXXXXX__________________________________________
Track Y,0 _____________________________XXXXXX______________________________
Track Y,5 ____________________________________________XXXXXX_______________

with TRACK ARCING you'll see
Or on

Track X,0 __XXXXXX__________________________________________________________
Track X,5 ___________XXXXXX_________________________________________XXXXXX_
Track Y,0 ______________________XXXXXX____________________XXXXXX___________
Track Y,5 _____________________________ ___________XXXXXX___________________

The resolution of the head is bad and can read sometime on half track but that's not a real reading, signals are nearest of strong noises than a good pulse
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JPL
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MessagePosté le: Mar 15 Jan 2008, 17:16    Sujet du message: Répondre en citant

vladitx a écrit:
my question still remains - is the stream continuous or not? If the software stops reading while head is moved it's still okay for imaging, but if the stream continues during the head movement process (in a quite bizarre curve) ... well, it becomes a little nightmare.


The write is not possible when arm move just because the phase1 of the step motor is connected to the WP signal ... and of course the LSS is a little upset when it believe the disk protected !

In othe words you can not write a spirale as on the old disks of music... you can just write some small parts on a track and move to the next track (half or quarter) to write an other part and so on... as result you have a disk hard to copy. because the head don't know where are the real good datas.
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vladitx



Inscrit le: 19 Déc 2007
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MessagePosté le: Mar 15 Jan 2008, 18:28    Sujet du message: Répondre en citant

EDIT: this one got somehow corrupted by ][ brackets Smile

Dernière édition par vladitx le Mer 16 Jan 2008, 1:06; édité 1 fois
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vladitx



Inscrit le: 19 Déc 2007
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MessagePosté le: Mar 15 Jan 2008, 18:29    Sujet du message: Répondre en citant

Thanks for the nifty diagram, JPL. It's exactly what I supposed them to be. I called them "partial tracks" since they're basically the same, whether the head moving or not in a single direction only.

JPL a écrit:
The write is not possible when arm move just because the phase1 of the step motor is connected to the WP signal ... and of course the LSS is a little upset when it believe the disk protected !


Making original diskettes shouldn't have been restricted to stock Disk2 drives or even Apple2. Bypassing the WP on phase1 is quite easy to do even by an amateur.

What case do you think LSS is upset? The only place I see shifting-in of the WP is during WP check, nowhere else.

JPL a écrit:
In othe words you can not write a spirale as on the old disks of music... you can just write some small parts on a track and move to the next track (half or quarter) to write an other part and so on... as result you have a disk hard to copy. because the head don't know where are the real good datas.


From the picture I assume that there was always pause in stream when moving the head, right? Unlike something like:

Code:

Track X.0:   XXXXXXXXXXXXXXXX----------------
Track X.5:   ----------------XXXXXXXXXXXXXXXX
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JPL
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MessagePosté le: Mar 15 Jan 2008, 22:35    Sujet du message: Répondre en citant

vladitx a écrit:

Making original diskettes shouldn't have been restricted to stock Disk2 drives or even Apple2. Bypassing the WP on phase1 is quite easy to do even by an amateur..


Yes absolutly easy and funny. http://www.hackzapple.com/DISKII/DISKIITECH11.HTM

vladitx a écrit:

What case do you think LSS is upset? The only place I see shifting-in of the WP is during WP check, nowhere else.



JPL a écrit:
In othe words you can not write a spirale as on the old disks of music... you can just write some small parts on a track and move to the next track (half or quarter) to write an other part and so on... as result you have a disk hard to copy. because the head don't know where are the real good datas.



The WP circuitry is activate by voltage of phase 1, for this reason Phases must be off when you write... and of course you can't write and move together. That's impossible, and I don't speak about the difficult to do a tracking of datas if it was possible.

vladitx a écrit:

From the picture I assume that there was always pause in stream when moving the head, right? Unlike something like:

Code:

Track X.0:   XXXXXXXXXXXXXXXX----------------
Track X.5:   ----------------XXXXXXXXXXXXXXXX


Yes absolutly right, it's the reason I draw a little space between areas of XXXX on two tracks. This in relation with the timing to go from one track to the next track... And you must have a little gap of synchronisation to read the "sectors"

XXXXXXXXX
----------XXXXXX
is impossible, you've an overlap

XXXXXXXXX
--------------tttSXXXXXX
is what you can do
ttt is the move of the disk when the arm move from one to other track
S are the nibbles for synchronisation to detect correctly the nibbles XXXX
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toinet
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Inscrit le: 15 Juin 2007
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Localisation: Le Chesnay, France

MessagePosté le: Mer 16 Jan 2008, 8:20    Sujet du message: Répondre en citant

vladitx a écrit:
Toinet, do you happen to have dissected Skyfox code?


Not done for Skyfox, Sir, but I have done it for The Seven Cities of Gold.

I will try to find it on my HDD...

antoine
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