Doug McNutt wrote:
I have had a lot of problems with "old" floppies. And it's more than loss of
information stored on them. Many just will not allow themselves to be reformatted. And
it's not just a difference with magnetic material on high density two holers vs low
density one holers.
I amuse myself thinking about just what environmental conditions might affect
the iron oxide coating. Altitude here at 6800 feet is one. Cosmic events like
solar magnetic storms and proton bombardment come to mind. Exposure to high
magnetic fields like speaker coils. Temperature variations. Dry desert
atmosphere.
But I do have 50 or so floppies that simply cannot be formatted. I can't find
visible defects with a microscope. Does anyone have any information on such
effects? Do floppies just get old in the absence of use?
I've always assumed it was just variable quality control on consumer
level floppy disks, with possibly declining quality as time went on.
Very nearly all of my 5.25" floppies from my family's Atari era still
work just fine, despite very rare use in the last two decades. Many of
my early PC 5.25" and 3.5" floppies from the early 90s still work fine
as well. On the other hand, my later PC and Mac 3.5" floppies are
possibly approaching a 40%-50% failure rate.
Generally, a genuinely unformattable disk has damage to track 0. Macs
and PCs do things a little differently, particularly where they give up
trying to format things. Macs will churn away formatting and checking
clusters until a certain total amount is bad (I forget the specific
amount, but somewhere around 1/3 the capacity of a HD floppy) at which
point it'll spit it out and declare it unusable. PCs on the other hand
will happily bad sector mark away the entire disk and leave it usable as
long as track 0 is ok. I think my record was a floppy with about 90k of
usable space left.
Don't really know any explanation for it all. Declining quality control
as the floppy era ended? Old disks that sat around in warehouses and
store shelves for years and were perhaps mistreated or subject to poor
climate control? Who knows.
Scott
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