On Mon, Feb 27, 2023 at 9:30 AM Chuck Guzis <ccl...@sydex.com> wrote:
> 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. > Prior to about 1984 or 85, the failure rate for DD floppies for me was high enough that I splurged for the QD. After 84 or 85, I never had any problems using DD media. I suspect that yields must have gotten better, but maybe I just had bad luck prior to going to college... > If one purchased factory-formatted diskettes for a specific platform, of > course the formatting would be different depending on the platform. > True. For the Rainbow I was always reformatting because nobody sold pre-formatted Rainbow disks at a price that was sane. > 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. > I believe that.. Warner
