5 1/4 diskettes available

On 7/10/19 7:14 PM, Fred Cisin via cctalk wrote: To add a bit to Fred's excellent explanation, I can offer the following: While the hub ring is *generally* a good indicator of "2D" versus "HD" disks, I've seen exceptions. Early 2D floppies did not use the hub ring and I've got a few HD ones that do. The hub ring thing is a story in itself, which I've gone into in the past. So, basically, what matters is how the cookie is punched and what the characteristics of the brown schmoo that it's been coated with. High-density diskettes use a coating that contains smaller particles, is generally thinner and of higher magnetic coercivity ("stiffer") nature. The punching has to do with "hard" sectoring vs. "soft" sectoring. In the former, as Fred mentioned, there is an extra hole (in addition to the index hole) in the cookie for each sector. Most 5.25" media is soft-sectored. You can tell the difference by holding the jacket of a floppy with one hand and rotating the cookie by the hub with the other. If you only see one hole appearing through the jacket aperture with every revolution, the disk is soft-sectored. Beyond that, you can forget the "tracks". The same floppy can be used in 80 track (96 track per inch) as well as 77 track (100 tracks per inch) as well as 40 track (48 tracks per inch) drives. 5.25" diskettes are only a bit more complicated than 3.5" ones, where you need only worry about the coating characteristics. Having said that, there *are* oddball exceptions, but you're unlikely to run into them in real life. 8" diskettes on the other hand, employ only one coating type, but use the index hole to indicate single-sided, vs. double-sided and density, as well as hard- vs. soft-sectoring and "flippy" floppies. Again, there are the "oddball" cases, such as the Vydec floppies that put the sector holes on the outer edge of the cookie or Memorex 650 disks that have a "dogleg" in the jacket outline, but you likely won't run into those. --Chuck