02-06-2016, 11:46 AM
(02-06-2016, 11:13 AM)keirf Wrote: However there are some pretty strict (read, stupid) protection formats on Amiga: I have one which reads 16 bits immediately following a sync word, and requires *those* to be non-deterministic. That's tough!
I think my simplistic PC FDC approach does usually show a change at the start of the data field, so there must be something there that is good enough. Though that does contain a write splice between 250Kbps format and 300Kbps format, so it's a bit unpredictable what you actually get when writing it. My common case only requires a difference somewhere in the sector data, which is much easier!
There is one Amstrad CPC case where there is a 4-byte signature followed by a 4-byte weak area that needs to change. That will require something a bit closer to what you're looking at for the Amiga, but it's still not as tight. Finding a reliable de-sync pattern would be good...
Another cheating approach I took for weak sectors was to duplicate them later on the track. When the software read it multiple times, it actually read different deterministic copies, which fooled it into thinking it was non-deterministic. That was needed for a motherboard with a buggy FDC, which couldn't handle my multi-pass formatting tricks. I don't know if that'd work for your Amiga case, or whether changing the original track representation too much would be undesirable.