27 Feb
2023
27 Feb
'23
5:30 p.m.
On Mon, Feb 27, 2023 at 9:30 AM Chuck Guzis <cclist(a)sydex.com> wrote:
On 2/27/23 06:50, Warner Losh wrote:
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...
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.
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