It is also worth noting, that although not all "360K" diskettes are up to
the task, they will still be much closer than "HD"/"1.2M" diskettes!
"360K" diskettes are 300 Oersted
"Quad density" diskettes are also 300 Oersted. The only difference is
that "QD" diskettes are tested for 96tpi, whereas "360K" diskettes are
tested at 48tpi. They are made of identical materials. However, if the
production quality control is marginal/poor, then you could have
some/many? that test OK at 48tpi, but are too flawed for 96tpi use. If
they are really good quality, then the 48tpi ones should work just fine.
OTOH, "HD"/"1.2M" diskettes are 600 oersted. Use of those for DD
300RPm/250Kbps / 360RPM/300kbps recording, whether at 48tpi, or 96tpi,
will result in data retention longevity that is lower than it should be.
Testing Roytype "HD" diskettes on TRS80 model 1 (SD/FM), gave data life of
MINUTES, whereas "360K" diskettes tend to last years
However, 3.5" "720K" diskettes are about 600 Oersted, and "1.4M" are about
720-750 Oersted. That is close enough that using the wrong media is
something that people often get away with.
I do not currently own a coercivity meter, so I can't check compliance
with the specs.
45 years ago, Verbatim made some very crappy diskettes. To recover from
their bad reputation, they came out with "Datalife" diskettes, which were
acceptable quality.
Dysan seems to have always been good. However, they "bet the company" on
3.25" disk form factor, and lost.
--
Grumpy Ol' Fred ci...@xenosoft.com
