Table of Content

This page is about the Atari protections mechanisms used on FD as well as the preservation for the future of Atari software provided on Floppy Disk Support.

Most, if not all, of the Atari programs are no longer available from their original suppliers and the problem with FD support is that the passage of time degrade them.

For programs released on floppy disks in the 80s / 90s we are now close to end of life for the media even if kept in good conditions. Preservation implies that unaltered representations of the original software are preserved.


Atari FD Copy Protection Mechanisms

This section presents some copy protection mechanisms used to protect programs on the Atari platform. Here I am mainly interested at discribing protections from a "harware point of view" (e.g. detail content of the FD) and not from a "sofware point of view" (how a program find about these protections and what to do with them).

If you are interested at the software side of the protections you can go to pages like Atari ST Protections from Markus Fritze or Les Protections sur Atari ST/AMIGA (in French) de DlFrSilver.

Lots of detailed information about copy protection by usage of key disk can be found in my document Atari Copy Protection Based on Key Disk. that describes hopefully most of the floppy disk protection mechanisms used on the Atari platform.

Program Protection Patents

In the area of protection of computer disc against unauthorized copying many patents exists. Some of them are presented below as they are of interest to understand Atari protections:

The following patent is not directly about Program Protection but is useful to understand the behavior of the FDC in presence of fuzzy bits as described in my Atari Copy Protection Based on Key Disk.

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Various Program Protection methods used on the Atari Platform

Many commercial Atari programs/games use some sort of protection mechanism to protect publishing companies from unauthorized copy of the originals. As for other platform the protection mechanism has evolved over time from very simple to very sophisticated. The protection mechanisms used on the Atari computers fall into three main categories:
  1. User Input based Protections
    This first mechanism is requesting the user to enter a series of letters and numbers at the start of (and/or even many times during) the program/game. This information was provided in "documents" that were difficult to reproduce in the 90s (remember that at that time scanners, color copy, etc.. where not available). For example the documentation could contain colored code that could only be read with special filtering glasses (red and green) or rotating wheels... This kind of protection is relatively cheap to produce and usually allow to install the program on a hard disk.
  2. Harware / Dongle Protections
    This second mechanism is to use an hardware key (also called a dongle) that plugs into an Atari port: usually the cartridge port but sometimes the joystick, or parallel ports. This kind of protection is relatively expensive to produce. It was therefore not used very much in games but was largely used by "professional" programs like musical programs from Steinberg (using dongles to plug on on the cartridge port). Normally programs protected with dongles can be installed on hard disks.
  3. Key disk Protections
    This third mechanism uses a "copy protected disk" or "key disk". In this protection the commercial software manufacturers uses specialy formated disk that can not be reproduced by a standard Atari system as a mean to protect their programs. By using special commands the software can verify that an original disk is used and not a copy. This verification is usually done at load time, and the program would refuse to run if the "protection information" was not correctly reproduced. The copy protection mechanisms on Atari started with simple tricks that could be reproduced by specialized software to end up with very sophisticated mechanism that requires special hardware (e.g. Blitz cable, Discovery Cartridge, KryoFlux ...). Some Atari protections are called: Copylocks (from Rob Northern), Speedlock, Macrodos, Short/Long Tracks, Fuzzy bits, ... Note that most key disk protected programs cannot be installed on a hard disk.
    For more information on this type of protection read my document Atari Copy Protection Based on Key Disk.

Note on usage of disk images format used for running protected programs / games with emulators:

You should also know that there are a lot of images of "cracked programs" available from internet. In this case of course the protection mechanisms are removed and a normal disk images can be used but this is out of scope of this page as this cannot be considered as preservation.

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Preservation Techniques available for Atari Users

Comparison of different Atari “preservation” techniques

The following table compares several techniques that can be used for preservation and/or backing-up protected FD (Key Disk):






KF Stream


File format











KryoFlux (1)

HW Cost/Avail.


Hard to find

Hard to find

90 €

90 €

SW Emul.



No (9)

No (11)

In dev (2)

HxC FD Emul.

Partial (3)

Partial (3)

No (9)

No (11)


Gen. file (4)



User (5)


SPS (10)

Preservation (6)


Yes not public




FD Backup

No (7)

Yes not public


Yes? (12)


Usage (13)





P/E/B (8)


  1. Kryoflux is only required for writing back to FD but not for usage with emulators
  2. According to SPS there is an emulator currently in test that support IPF files
  3. It is not clear that the current HcX devices can read all STX files
  4. "Gen. file" indicates who is able to generate the output file
  5. In order to produce correct output file the user need to use or create a control script. There are control scripts available for several hundred of protected FD in the public domain but new script cannot be added by the now dead company.
  6. The meaning of preservation is a never-ending debate that I do not want to open here! Let’s just say a flux level imaging devices is required if you want to be able to recreate a FD as close as possible of the original
  7. Writing FD from Pasti STX is probably feasible in most cases. However the resulting FD, even if it would produce results similar to original when running in ST, will most likely be quite different from original FD and therefore should not be considered as preservation.
  8. According to SPS people the main usage of the IPF files is for preservation. But IPF files can also be used by SW emulators (work in progress), HxC FD Emulator and to write back FD (work in progress).
  9. It should be possible to use the DC mfmbtemp file format for SW or FD emulators. However I doubt that this project will ever happen!
  10. Only SPS people or specially trained people using expensive CTS software can produce IPF files.
  11. It would be possible to use the KryoFlux Stream/Draft file format for SW or FD emulators. But there is no plan that I am aware.
  12. At this stage it is unclear that the Stream/Draft files can be used to write back directly protected FD.
  13. Usage: Can either be E=Emulators (hard or soft), P=FD Preservation, B=FD Backup (FD copy)
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What solution should I use?

The solution depends of your primary usage:

For example most if not all the valuable programs that I have bought, especially for musical composition, have been preserved and duplicated. I did the same for few games that I did not want to lose (e.g. Dungeon Master). I have done all these preservations/backups back in the 90s using the Discovery Cartridge. Therefore for all these programs I have at least one FD backup and therefore I never use the original disk. I have also kept images of the FD on hard disk that allow me to recreate a new FD if necessary.
When I want to run one of these program on an emulator I use an STX images of the original program.

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Backup / Preservation of Protected Disk

Backup Philosophy

A backup program should always do the most to ensure the integrity of the resultant copy. The copy produced should operate just like the original and not remove the protection, or modify the program being copied in any way. The backup program must do the up most to check that the copy produced is correct, with correct checksums. Therefore analog copiers should be avoided.

Note that in order to create a backup of most Atari copy protected FDs, special hardware is required. This is because many of the protection mechanisms cannot be reproduced directly using the Atari FD controller. One of the best hardware solution for creating backup of Atari diskettes (protected or not) used to be the Discovery Cartridge from Happy Computer. It uses a specially designed IC that allows to work down at the flux level when necessary and therefore can handle all possible Atari ST protection mechanisms. A new solotion has been designed recently by KryoFlux Products & Services Limited. You can find some information about it on my site here.

There are several Atari ST FD imaging formats for non protected diskettes (ST, DIM, MSA, ...) which were mainly created for emulation purpose but can also be used to recreate diskettes (backup).  There are also few imaging formats for protected diskettes (STT, STX, ...) which can be used to run program on emulators, however it is not (yet) possible to recreate FD from these images. For example the PASTI Preservation program provide the capability to create disk images (STX format) of almost all protected FD. These images can be used to run on emulators like SainT and STeem.

Typical procedure for duplication of protected diskettes:

  1. Create a disk image of the diskette using a format that can record all information including all copy protection mechanisms used by the Atari key protected diskettes. Currently only the Discovery Cartridge or the Kryoflux board allow to create such images.
  2. Write a backup of the diskette using the disk image created in the first step. As already mentioned this usually requires to use specialized hardware (at least for many protections) like the Discovery Cartridge or the KryoFlux Device.

Note that this duplication procedure is exactly what is used by the Discovery Cartridge backup program. But unfortunately the DC backup program requires information about the protection from the user and is therefore not fully automated.

You will find here an Excel table (without any warranty) that contains a compilation of about 950 entries of program/games diskettes and the best known way to copy them using software copiers and blitz cable.

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Software Copiers

The Atari TOS provide a rudimentary backup program using a simple drag and drop procedure. However this duplication only works for "standard" TOS formatted floppies and will fail for anything not standard (e.g. with different number of sector per tracks, with non standard 512 bytes sectors, etc.). This limitation (non standard layout) was used as a simple protection mechanism .

Therefore many specifically designed software copiers were developed to bypass some of the protection mechanisms. Several of these backup programs are pretty good at copying games FD that uses many "weak" protection mechanisms: AC13A, AC12E, DSAPIENS, FASTCOPY 1, PROCOPY 1.5, STARCOPY, STCOPY20, STCOPY 7.65 (you will found most of them in this archive) or the well known Fast Copy Pro.

But as said before some protections like fuzzy bits cannot be copied using only software.

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Hardware Copiers

As soon as an Atari FD uses more sophisticated protection mechanisms it is necessary to use a "Hardware Copier". There are two type of HW copiers:

While analog copiers can be used to produce working copy of protected games they do not fulfill the backup phylosophy requirements as described above and therefore they should be avoided if possible. For sure they cannot be used for preservation.

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The Blitz Analog Copier

The Blitz solution is an hardware analog copier composed of a special cable and an associated program. It is good at copying many protected diskettes, but certainly not equivalent to a digital solution like the Discovery Cartridge or the KryoFlux board.

Blitz presentation:

"BLITZ from AT YOUR SERVICE is a revolutionary new back-up system for the Atari ST computer. BLITZ uses ONLY a special cable and software to back-up your software at a speed and power unheard of before. There is NO internal wiring done to the computer. The BLITZ cable copies from Drive 1 out through the Computer printer port to drive 2 (You must have two drives to use BLITZ). It reads Drive 1 and writes Drive 2 at the same time. The time it takes a normal copy program to read a disk, the BLITZ reads and writes the disk in one pass. The BLITZ backs-up protected and non-protected disks in the same amount of time"...

This solution allows to backup many protected games, but fails on others. Basically the blitz solution copy the analog data from one floppy drive directly to another floppy drive without using the FDC (the floppy drives are actually controlled through the parallel interface). Therefore it is suppose to handle many protection mechanisms that play with the bitcell timing (e.g. writing floppies with non standard drive speed, etc...). However this is not a perfect solution as it does a "blind analog copy" of the flux without performing any control or check and the process is very sensitive to drives speed and synchronization. Nevertheless it works fine in many cases even if the resulting image is certainly not a "perfect copy" (i.e. it is usually not possible to make copy of copy). If you want to try this solution you need to buy or build a BLITZ cable and use the special BLITZ program (original disk). The following archive contains other versions of blitz programs that I have collected. You will need to experiment these different versions as some works better than others for different protected diskettes (refer also to this Excel table).

What to think about Analog Copier

Here is a quote on analog copier from Fiat of the SPS project:

Although the data stored on floppy disks is digital (being computer data) it is is stored in an analogue form. In hardware copiers the computer reads the disk by interpreting the bitcells making up the flux transitions as 0's and 1's, checks all checksums match and holds that data to be subsequently written. It is "refreshed" and so "new" every time it is written. However, in analogue copiers, there is no such buffering. They work by tightly synchronizing two drives and the signals send from one disk to another is a pure analogue signal. There is no checking of integrity (CRC, etc.), because the data is never actually "processed". This is the only practical way a consumer can try to copy protected disks and such a solution is cheap to develop and manufacture. A disk copy produced by such a process is slightly less "quality" than the master. If you keep making generational copies like this the copy gets worse until the bitcells can no longer "hold together". Unfortunately, since it is digital data the result is that you get errors (bits are mis-read and even "bit shift", that is, corrupt neighbor bits because of their change of value), and likely the game will not work any more. The trick to understanding the above is that what is recorded on floppy disks is not just the data, there are other sorts of information too. They can copy many density protections, just as long as the timing is not too strict (for example, the Amiga version of Rob Northen's Copylock usually fails, and the ST version is quite similar). They can also copy disks with variations in disk format. However, they cannot copy flakey bits (aka weak bits). You cannot blindly image this protection, because of the way it works. See here for more information: flakeybits. This type of protection looks so far very common on the ST and PC.

Here is a quote from Ijor on analog copier :

Disk analog copiers work very similarly as dubbing an audio tape. They just reproduce the signal from the source diskette into the destination one. The consequences of this are several:

Personal note:

I think that the term analog copier is a bit confusing as the interface of the FD drive is digital (i.e. TLL signal) and therefore we are not really dealing with analog signals like it would be with an analog recorder (e.g. VCR). However, if clearly specified and understood, the term analog is acceptable to indicate the fact that the signals produced by the head of the reading device is not processed by a digital circuit (the FDC) but directly sent to the head of the recording device and therefore it is not "regenerated". Due to the nature of the analog signal coming from the head the shape (and therefore most importantly the timing) of the converted digital signal will be quite different from the original signal and will definitively degrade during multiple copies.
But I disagree with the fact that analog copier cannot copy weak / flaky bits, actually they should be relatively good at that ... however as already said they do not fulfill the backup phylosophy requirements.

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Atari Protection References


As many of the documents refenced here are difficult to find, you will find a local copy of these documents.

Forums Threads

Web Links

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