Copy Protection Information: Weak Bits, Bit-rate ...

A forum about Atari protected floppy disks analysis, preservation, emulation, tools

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Postby DrCoolZic » Sat Jul 29, 2006 7:36 pm

ppera wrote: http://www.ppest.org/atari/floimgd.php
Some things what can not be done with ordinary Atari can be done with PC...
I can give you more details about...

Yes I (and probably others) would definitively be interested to learn more about what you can do with your program (did not had time to look at it yet) on a PC that cant be done on an Atari.

ppera wrote: I need some cooperation in making program floimg better. Ideas about disk image formats, what records/fields in them, how to present weak sectors and similar.
...

Actually I am also interested in "having" a disk image format for protected / non protected Atari ST diskettes something similar to the work done for Atari 16 bits (see http://members.chello.nl/taf.offenga/ap ... /ATP16.htm )

I beleive that the best would be to use the PASTI format as it already exist (as well as hundreds of images) and is suppose to handle all known protected diskettes. For that matter the format needs to be fully described and public. From what I understand I think that Ijor is not against this idea but would like more time ... but of course Ijor is the right person to comment this ...

As some protection mechanisme cant be duplicated with the FDC on an Atari or on a PC there is also a project to recreate diskettes from PASTI format using the Discovery Cartridge Hardware on Atari ...
Last edited by DrCoolZic on Sun Jul 30, 2006 2:11 pm, edited 1 time in total.

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Postby DrCoolZic » Sat Jul 29, 2006 7:42 pm

Zorro 2 wrote:Very excellent job mister DrCoolZic !


Thanks. This document is in fact part of a bigger document that I wrote about FD on Atari.

As I already mentioned I am interested by the subject of duplication of Atari ST protected diskettes. Therefore I wrote this document (actually a non published web site) to have all this information handy ...

If there is interest I can publish the complete document?

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Postby DrCoolZic » Sat Jul 29, 2006 8:08 pm

ppera wrote:About copy protection document:
... section standard floppies ...


In the document what I refer as "standard floppies" are floppies that can be duplicated by using the "standard duplicate procedure" from TOS (i.e. dragging floppy a over b). If am correct only 9 sect/Trk is supported by this TOS procedure. Duplication of diskettes with any other format requires speciffically design "copier" not provided by Atari and/or DRI.

ppera wrote:In praxis that means that floppies with 1 to 22 sector/track are usable. It is checked, not theory....

Humm ?!? As far as I know FD with 29 sectors of 128 bytes works fine on Atari.

ppera wrote:One thing more: developers at Atari or DR made strange solution by floppy format - they choosed FAT size of 5 sectors, instead 3, what would ensure PC compability by 720K floppies. I have no idea what may be reason.

True FAT on PC usually uses 3 sectors and FAT on Atari uses 5 sectors. However I do not see why this should be of any problem with PC???
To be sure I just checked with the MS-DOS Programmer's reference book (version 5.0 1991): look at the bootsector field bsFATsecs => it specifies the number of sectors occupied by each FAT. If you combine this field with the bsFATs (number of FAT) it allow to compute the location of the root directory and this is all you (I mean the OS) need... So any size for the FAT is fine as long as information of the bootsector is correct.
I guess that at that time DRI did not have enough historical information to know that it was a (small) waste of FD space

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Postby Mug UK » Sun Jul 30, 2006 9:11 am

DrCoolZic wrote:If there is interest I can publish the complete document?


That is what our Wiki is for. Find a section it will fit into (or create your own) and I, or others, can help with the English side of things if you want to update it in your own language plus an English one.

That's what we're all here for ;-)
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Postby unseenmenace » Sun Jul 30, 2006 2:19 pm

DrCoolZic wrote:In the document what I refer as "standard floppies" are floppies that can be duplicated by using the "standard duplicate procedure" from TOS (i.e. dragging floppy a over b). If am correct only 9 sect/Trk is supported by this TOS procedure. Duplication of diskettes with any other format requires speciffically design "copier" not provided by Atari and/or DRI.

If I remember correctly the GEM disk copy routine can in fact copy any non-copyprotected disk but the destination disk has to be already formatted to the same settings as the source disk.
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Postby ppera » Mon Jul 31, 2006 9:54 am

DrCoolZic wrote:I If am correct only 9 sect/Trk is supported by this TOS procedure. Duplication of diskettes with any other format requires speciffically design "copier" not provided by Atari and/or DRI.
ppera wrote:In praxis that means that floppies with 1 to 22 sector/track are usable. It is checked, not theory....

Humm ?!? As far as I know FD with 29 sectors of 128 bytes works fine on Atari....


Floppies with 10 sectors/track can be easily copied with Desktop. And 1 sec/tr. too, and 15 too. 29 not, but reason is that only sector size of 512 byte is supported.

Don't mix 'working fine' with 'may be done with ROM, Desktop'.

I talk all this from praxis. I made some software for copiing/formatting on ST. I did not get in copy protections in that time much, but about 'standard' formats is all clear. Question is only how you will explain it for masses.

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Postby DrCoolZic » Mon Nov 20, 2006 10:18 am

A have completed a new version (0.4) of the Atari FD protection mechanisms.

First I have made few minor changes like: merging of related protections, improvement of several protection descriptions, new protections (some not yet completed), lots of clean-up, etc.

However the most important changes are around the bit-rate variation/violations… In this area I have conducted a lot of experiments. More specifically I have analyzed games/programs that uses the short/long bit-cell width / block width (e.g. Populous using Rob Northen), Fuzzy bits located at border of inspection windows (e.g. Dungeon master, Populous), and large bit-cell width violation (e.g. DrT D50 Editor).
In order to conduct these analysis I have used my "analyze program" that I have drastically modified in order to get precise and more detailed information. The most significant change that I have made to the program concern an implementation of a DPLL equivalent to the one used in the WD1772 (I had never been satisfied by any of my previous implementations). Effectively I learned recently that the WD1772 DPLL was based on an US public patent . The paten is rather complex but extremely interesting and detailed (see the document for more details). The result is that the decoding of the bits as recorded with a Discovery Cartridge (62.5 ns precision) provides results extremely close to a real Atari.

I have adjusted the descriptions based on these new experiments but more importantly I have added a completely new section that describes in great details these different protections illustrated by outputs from the analyze program. I have also added a short presentation on the analyze program that provide just enough information for you to interprets the outputs of the program/games analyzed.
In order to fully understand the fuzzy bits it is also necessary to have a basic understanding of the WD1772 DPLL and shift register and I have added a short section for that matter.

So hopefully you should be able to learn “everything you always wanted to know about fuzzy bits but never dare to ask…”

The next steps planed are to fully analyze the “data over index” and some special protections like the one used in Turrican … Stay Tuned ...

As usual I am interested in getting feedback to correct errors, ambiguities, etc.

Jean
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Postby DrCoolZic » Wed Nov 22, 2006 5:25 pm

Attached is a spreadsheet of over 900 programs/games that indicates how to copy the orginal diskettes (only SW copy and analog Blitz copy). I got this listing from a bundle deal I made recently, I have scaned the original document but did not perform any test. In the deal I also have received several hundreds of "copied" diskettes, but did not had time to look at them.

I did not check any of this information and therefore not sure it is very useful. I hope to be able to create such a list with detail verified info later on.
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Postby gothmog » Wed Nov 29, 2006 6:59 pm

On the US Patent and Trademark Office web site http://www.uspto.gov/ you can view patent #4849836 which describes the copy protection used in Dungeon Master.

You can also view an easier to read version here:
http://dm.dfxdx.co.uk/?showPage&PAGEID=19

Maybe this can help you for your document?

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Postby DrCoolZic » Wed Nov 29, 2006 7:12 pm

gothmog wrote:On the US Patent and Trademark Office web site http://www.uspto.gov/ you can view patent #4849836 which describes the copy protection used in Dungeon Master.

You can also view an easier to read version here:
http://dm.dfxdx.co.uk/?showPage&PAGEID=19

Maybe this can help you for your document?


I just browsed quickly and it seems very interesting. I will look at it carefully.
Thanks for the information.

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Postby Greenious » Thu Nov 30, 2006 3:28 pm

DrCoolZic wrote:A have completed a new version (0.4) of the Atari FD protection mechanisms.


Just stumbled in here, and found this. Very interesting, thanks for your efforts.
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Postby Mug UK » Thu Nov 30, 2006 3:53 pm

I hope he made something out of it .. don't understand half of what's on there but it's nice to see some people patenting stuff like this in the old days.

Wonder if Rob Northen ever did anything similar?
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Postby Greenious » Thu Nov 30, 2006 5:10 pm

I must say I find this topic very interesting. From a hardware point of view. :)

Since I finally seems to have tracked down the last parts I need for some serious STE hacking, aswell as ST version down the road, (adding fastram, 16mhz accelerator with cache, IDE interface, FPU, and a few other small additions), I'm looking around for something to top it off, making it unique.

Ideas I have range from a integrated DAC, to add sampling capabilities, to some generic co-cpu or interface.

A request from marcer mentioned some additional musicchip. (although I don't know what that would be, a C64 SID? another ym2149?)

The point is not to make an all out board right off the bat, but more design issues of the boards that would make those additions easier later on.

Anyway, with discovery cartridges scarce, one idea would be to have some sort of fdc that indeed can replicate any disk. Maybe, with a 16mhz accelerator with fastram, a lot of timing can be made with software, and the logic could be kept very simple.
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Postby DrCoolZic » Thu Nov 30, 2006 5:18 pm

Greenious wrote:I must say I find this topic very interesting. From a hardware point of view. :)
...
Anyway, with discovery cartridges scarce, one idea would be to have some sort of fdc that indeed can replicate any disk. Maybe, with a 16mhz accelerator with fastram, a lot of timing can be made with software, and the logic could be kept very simple.


Interesting you mention that ... I also had thought of a nice project along those lines ... I even came with a name for it: dc++ as it would be a super DC with much more features ...

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Postby ijor » Thu Nov 30, 2006 6:21 pm

Greenious wrote:Since I finally seems to have tracked down the last parts I need for some serious STE hacking on...
Anyway, with discovery cartridges scarce, one idea would be to have some sort of fdc that indeed can replicate any disk. Maybe, with a 16mhz accelerator with fastram, a lot of timing can be made with software, and the logic could be kept very simple.


I don't see much point in replicating the DC, or making something similar. It would be much better to make a PC device (and compete with the Catweasel), or an external USB device.

Of course, if you are making a powerful (and not so cheap) major hardware upgrade already, then adding "DC like" capabilities might not increase the costs too much. And then, even when not as useful as a PC solution IMHO, you don't loose too much either.

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Postby ijor » Thu Nov 30, 2006 6:23 pm

DrCoolZic wrote:I even came with a name for it: dc++ as it would be a super DC with much more features ...


Really? What the standard DC hardware is missing? I agree that lot of things could be added/improoved to the software. But to the hardware?

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Postby DrCoolZic » Thu Nov 30, 2006 6:59 pm

ijor wrote:Really? What the standard DC hardware is missing? I agree that lot of things could be added/improoved to the software. But to the hardware?
As far as I know nothing realy ... but as Greenious mentioned
Greenious wrote:Anyway, with discovery cartridges scarce, one idea would be to have some sort of fdc that indeed can replicate any disk.
It is becomming difficult to find DC hw and building a new solution would solve this problem, plus will give full control over features and software. Should not be that difficult using an FPGA/CPLD ...
just a thought ...

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Postby DrCoolZic » Thu Nov 30, 2006 7:10 pm

gothmog wrote:On the US Patent and Trademark Office web site http://www.uspto.gov/ you can view patent #4849836 which describes the copy protection used in Dungeon Master.
I have read in great detail the patent and yes it must be the one used in DM (how did you find out?).
It explain well the idea of the fuzzy bits and provides several possible ways to create them. Of much interest of course is the way to create them as described in figure 2 and text column 3 lines 30+: A sliding edge at the border of the bit boundary. This exactly related to what I have described in my document in the fuzzy bit section. But it add a nice touch: a slowly sliding bits that will for sure result in fuzzy bits ...

This is great I will update my doc based on that ...

Ps the other method for getting fuzzy bits are much more difficult to realize and I do not think were used for Atari diskettes?

Thanks again mr Gothmog

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Postby Greenious » Thu Nov 30, 2006 7:28 pm

ijor wrote:I don't see much point in replicating the DC, or making something similar. It would be much better to make a PC device (and compete with the Catweasel), or an external USB device.


Those things are projects by themselves. Maybe I have a go at something like that later, although I doubt it.

Of course, if you are making a powerful (and not so cheap) major hardware upgrade already, then adding "DC like" capabilities might not increase the costs too much. And then, even when not as useful as a PC solution IMHO, you don't loose too much either.


That's the point. The board I'm already designing will have a FPGA/CPLD that is overkill for the project (most costeffective), adding some simple functions to add extra rom select lines for future expansions & a small expansionbus will add like... a buck or two to the total cost of the project anyway. Heck, if all you need is a few direct controlled i/o pins, it could just as well be implemented from start.

What would be most fun for me though, would be to add something for people to explore, something the hackers end up using for things I can't imagine. Something that get's peoples curiosity going again, and is so cheap, that people not getting my board, end up adding on their own to their atari, just because it is so much fun/add so much functionality.
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Postby DrCoolZic » Thu Nov 30, 2006 7:45 pm

By the way Greenious
The project you are talking about what is it exactly? Is there a description available somewhere???

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Postby DrCoolZic » Thu Nov 30, 2006 8:01 pm

ijor wrote:I don't see much point in replicating the DC, or making something similar. It would be much better to make a PC device (and compete with the Catweasel), or an external USB device.

Exactly ! Talking about DC++ I was not refering to reproduce the DC on an Atari but more like a universal and personal "Trace Machine" (without the cost) that would allow to reproduce any floppy from any machine.

Say for example a box that connect to an USB port with programs that range from fully automatic (for dump user copy) to full control for expert ...

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Postby ijor » Thu Nov 30, 2006 8:08 pm

Greenious wrote:That's the point....Heck, if all you need is a few direct controlled i/o pins, it could just as well be implemented from start.


You need more than just I/O pins. But nothing that couldn't be implemented in a small FPGA/CPLD. Perhaps the most expensive aspect is the ROM stuff (remember what we talked about in the overscan thread). But you don't need to execute from ROM if you have fast RAM. I'm not sure, but with the knowledge that we currently have about pairing, it is possible that it could be done running from plain RAM. But without ROM you lose DC compatiblity, which is a good thing to have.

What would be most fun for me though, would be to add something for people to explore, something the hackers end up using for things I can't imagine.


If you ask me, something that I would like is a programmable ripper/freezer. That is, something like the Ultimate Ripper but with flash instead of EPROM. Or even better with NVRAM, or anything that you could easily rewrite as much as you want. Actually even volatile RAM could be good enough, because you can cold boot without power cycling.

A step forward with the same idea would be a programmable TOS. Again, in flash, NVRAM, or just RAM.

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Postby ijor » Thu Nov 30, 2006 8:16 pm

DrCoolZic wrote:But it add a nice touch: a slowly sliding bits that will for sure result in fuzzy bits ...


It is not a nice though, it is required to get the desired result using this technique. If you just make the transitions fixed on the middle range, then the result would depend on the drive.

Ps the other method for getting fuzzy bits are much more difficult to realize and I do not think were used for Atari diskettes?


I didn't read it detaily, but if you are talking about using track misregistration, or physical alteration for producing weak bits, then AFAIK not.

Thanks again mr Gothmog


Thanks indeed. I wasn't aware they were granted a patent. Strange, I'm not sure, but I think they weren't the first neither the last using this technique.

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Postby gothmog » Thu Nov 30, 2006 9:33 pm

I did not find the patent myself, the webmaster of http://dm.dfxdx.co.uk/ found it.
By the way, I am the webmaster of the DM & CSB Encyclopaedia http://dmweb.free.fr/. Thanks for the link to my website in your document. I guess I will have to update my web page about the copy protection with information from your document and the patent.

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Postby ijor » Thu Nov 30, 2006 10:19 pm

DrCoolZic wrote:A have completed a new version (0.4) of the Atari FD protection mechanisms.
...
As usual I am interested in getting feedback to correct errors, ambiguities, etc.


I intended to make some comments. But seems you protected the PDF, then it is quite cumbersome, because I would need to retype every quote :(


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