DrCoolZic wrote:As you know there many games that use what I call shifted tracks.
Usually very hard to reproduce on real Atari and also causing problem for HW duplicators
If I remember correctly if you replicate all the sector but the track is not shifted the protection fails.
I would like to know how this is checked. It could be by measuring time to find position of specific sector on track but more probably by making a read track and looking at layout.
npomarede wrote:DrCoolZic wrote:As you know there many games that use what I call shifted tracks.
Different methods could be used :
- if all tracks contains sectors 1 to 10 in the same orders, then you can do a "force interrupt on index pulse", then immediately after do a "read sector 1" and measure how many time it takes to complete. Knowing the initial shifting algo and the current head's position, it's then easy to see if the delay to read sector 1 matches the expected layout.
DrCoolZic wrote:If I understand correctly time between index and end of read last sector? This should be more than 200 ms
In shifted track I have seen extreme cases:
- ID field starts just before index. So with normal read track you may miss the ID because char stuck in FIFO
- One that caused problem with Aufit was one or two a1 sync mark before index and real start of ID just after index!!! On real Atari do not expect to see anything for reason above.
And in emulator it is a pain because if you start "decoding" flux at index you wont find the fisrt sync mark and therefore just ignore the first ID
One of the reason you need multiple revolutions sampled
Computer Hits Volume 2 (Beau Jolly) one to two sync mark on all tracks of disk 2
DrCoolZic wrote:I have updated the Atari FD protection document to version 1.3
kodak80 wrote:Jean, the links don't seem to be clickable for me in the PDF. They are showing as blue and underlined but I cannot click on them to open the associated links.
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