What are the differences among single, double, quad, and high density floppy media?
There is essentially no difference between single and double density media (if you can actually find any single density media anymore). Double density media has been tested and certified for double density recording, which is slightly more demanding than single density recording; conceivably, a dropout that might not be noticed in single density could be a problem in double density. In practice, though, I suspect that back in the days when manufacturers sold both DD and SD media, the media came off the same production line and the SD media would have met the DD standard nearly all the time. “Quad density” 5.25-inch media is certified for double density recording at 80 tracks per side rather than 40 tracks per side. This is quite different from “high density,” discussed below. 80 TPS quad density media should work fine at 40 TPS double density. I’ve been told that there can be problems using 40 TPS double density media at 80 TPS quad density; I believe the person who told me this, but n
