27 Feb
2023
27 Feb
'23
4:30 p.m.
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