On 2/27/23 06:50, Warner Losh wrote: > You should be using QD floppies, but those are rare. DD floppies from > later than > 1985 though work just fine (discovered empirically while a poor college > student, > reconfirmed recently when I made all those Venix disks).
Speaking from experience and consultations during the 1970s with engineers from Dysan (we were using 100 tpi drives), the only difference between QD and DD floppies is QA step--QD ones are usually verified at 96 or 100 tpi, the DD ones at 48 tpi. The brown goo spread on the doughnut is exactly the same. If one purchased factory-formatted diskettes for a specific platform, of course the formatting would be different depending on the platform. Similarly SS and DS diskettes are identical; early on, ones with verification errors on one side were "flipped" accordingly and sold as SS. As techniques improved, the only difference became the label. FWIW, Chuck
