obo wrote:I have to admit I sometimes find ijor's responses a little frustrating. He has contributed a lot to the Atari community, and does have great experience of this subject, but sometimes it's a bit difficult to tap that knowledge. He'll correct your mistakes and answer specific questions, but you'll probably not get much beyond what you've asked without asking a new question.
Oh, so now there are two against one. I give up
Seriously, what do you expect? What would you like "beyond"? Do you expect me to answer with a whole book covering all possible FDC/Pasti/Protections/disks related topics? Do you expect me to guess
what you would like to ask but you didn't, or what you might be possibly interested to know?
Information on specific ST protections has been very hard to find...
There are virtually no ST specific protections. They are almost all generic and would apply to any similar system. Most of them are even completely generic and apply to any system.
The topic is not the most easily to find on-line, but it is not impossible. There are even a couple of ST specific books. The books are a bit outdated, and probably don't cover the latest protections developed in Europe. But those ones are widely known and I think you are already quite familiar with them.
If you wanted me to publish a structured table of all the possible ST protections, then I am afraid I have no such a thing. Not even something partial or close to that.
The only thing I could elaborate about this is the possible concepts of protections. You just need to think what a user system can't reproduce. From the top of my head, they are:
- The lack of the FDC capability of writing some bytes at format time.
- Weak bits.
- The fact that the FDC uses a fixed and constant bit-rate.
- Strong DC erased.
- Physical alteration of the disk surface.
Note that only the first one is somehow (but not completely) ST specific. Actually it is not even ST, but WD FDC specific.
There are of course a big number of simpler protections that the FDC does can reproduce. They can be as simple as just not using a standard FAT filesystem. I suppose this is not what you are interested.
There are a coutless number of variations and combinations. And I'm sure that Jean studied them in more detail than I did.
I'd really like to know more about what was required to simulate some of the PASTI images, as that would require knowing the specifics of each protection. Even knowledge of what the specific protections check on the original disk would be useful, so reproductions could aim to satisfy those without needing to reproduce every flux transition on the original.
As I said already, the Pasti tools have virtually no knowledge about the specifics of each protection. They just know some generic concepts. For example, the imaging tool measures timing for each sector. Then the DLL reproduces the timing. The DLL is not aware (it could be in theory, but it does not) if the sector or track you are reading is protected or not. It just reproduces the behavior read by the imaging tool.
This is by design, to be able to deal with protections and combinations that I didn't expect.
The Pasti images don't have a protection code or number. That is, there is nowhere in the image a mark saying, this is CopyLock, or something like that. I don't even have an internal database of which protection is used on each game. So that when somebody asks me that, then I have to make some analysis of the image for answering.
I think that 90%, possibly more, of this post I already answered to you in email, posted here or somewhere else in the forum. So as you can see, I don't have anything else as you seems to be expecting. So I am afraid if something is still missing, you would need to ask explicitely
Happy New Year