RFC: Floppy reader/writer project (recovering UniPlus Unix for the Lisa)

dwight elvey dkelvey at hotmail.com
Thu Feb 21 23:43:21 CST 2008


> From: jules.richardson99 at gmail.com > Chuck Guzis wrote:> > In my humble opinion, what's really needed is a quick and reliable > > non-contact method of recovering floppy data. Perhaps one of the > > more modern head technologies, such as GMR might be suitable for a > > head that doesn't contact the media.> > Would a non-contact head 'fly' properly at floppy speeds, though? (I'm not > sure how much more rotational speed you could get out of a floppy, even > jacketless - I suspect the media is just too flexible)> > > Or maybe we need to revive the "magnasee and laser" method.> > Would magnasee work usefully at floppy bit densities? I thought it was mainly > intended to detect track-level problems and large areas of damage, but could > easily be wrong there.> > > Increasingly, I'm seeing 5.25" diskettes with media flaking. > > It might be that we're starting to approach the "use by" date with > > some brands and need to resort to other approaches.> > I keep wondering about running the whole lot - disk and drive mechanism - in > some 'bath' of something-or-other. It's another matter whether it would a) > help and b) work at all :-) Anything which keeps friction/heat between the > disk and heads to a minimum seems like a good idea, though.> 
Hi
 Some of the newer hard disk heads use a head that doesn't require
a speeding head to read. It is like a hall effect in that it measure total
magnetic field. It isn't like a hall effect in that it snaps from one state to
another. The advantage is that it isn't speed sensitive, just level.
 I forget what this type is called. One could raise and lower it along
the track, never scrapping the surface, just sampling. One would turn
a 1/4 bit at time and sample that location. One would then record any
pulse, indicating a flux reversal.
Dwight
 
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