amiga floppy disk reading experience

Without sounding too obvious here, the time between the pulses (which more or less define the data) were grossly out of spec. The DD pulses should nominally be 4us, 6us, and 8us apart before pre-write compensation. Most good disks are slightly faster, and normal times for these ranges are: 4us: 3.2-4.2us. Many around 3.75us 6us: 5.5-6.2us. 8us: 7.5-8.2us (notice margins around 1-1.3us) My original microcontroller implementation was 3.2-4.2, 5.2-6.2, and 7.2-8.2. When my current FPGA controller would have a problem, I'd notice that there were problems right on a boundary. So maybe pulses were coming in at 3.1us apart instead of 3.2. Or maybe 4.3 instead of 4.2. So I kept bumping the intervals apart, making a larger range of pulse times acceptable --- the XOR sector checksums were passing, so I was likely making the right choices. The bits were ending up in the right buckets. But as I went through some of these disks, I ended up with the difference between ranges(and basically my noise margin) being reduced smaller and smaller. Some to the point where an incoming pulse time might fall darn smack in the middle of the noise margin. Which bucket does THAT one go into? My approach has been very successful(easily 95%+), but it makes me wonder about Phil's DiscFerret dynamic adaptive approach where a sample of the incoming data defines the ranges.