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Re: Floppy stuff [was Re: What is the dd command ???]

On Wed, May 03, 2006 at 02:02:10PM -0500, Mike McCarty wrote:
> Andrew Sackville-West wrote:
> >On Wed, May 03, 2006 at 12:34:59PM -0500, Mike McCarty wrote:
> [snip]
> >>Be sure that one of your discs is a 720K disc, and has been degaussed.
> >>BTW, if it Just Works on high-mu discs, even when never formatted,
> >>then I suspect that it will ruin your 720K disc. So make sure it's
> >>one you don't mind losing. 
> >
> >
> >Agreed. though, as long as the magnetic media is intact, would not a
> >low-level format "Rescue" a disc? not the data, but the usability of
> >the disc. 
> Probably not. Degaussing it properly would. But once the disc
> has been magnetized with hi-coercion magnetic fields, attempting
> to reformat it using lo-coercion fields fails in my experience.

\light goes on\
aha! I follow. thanks.

> >>I know I've got some 720K discs around
> >>somewhere, one of which I could sacrifice...
> >
> >
> >I don't have any of those :(. Further inspection also reveals that my
> >floppies were formatted at the factory (says right on 'em, heh). And,
> >after all these years of being careful with floppies, I can attest
> >that its not so easy as you'd think to degauss a floppy. Things I've
> It only happens when you *don't* want it to happen.


> >tried so far:
> >
> >big magnet on a 15" speaker
> >microwave (he he)
> I'd think that would burn it up, not degauss it :-)

a quick google search turned that up as a possible way to degauss a
disk (including such other dubios methods as putting it in a vacuum
cleaner). The reasoning was that the microwave would have a
sufficient field strength to do it. Not. But if you leave it in long
enough the metal shield over the access port will arc to the
hub. That's pretty exciting!

> >ac motor on my drill press
> >various fridge magnets wiped over the surface
> >holding on my monitor while degaussing the monitor
> >
> >sheesh.
> >
> >somewhere around here I have a degausser for cassette tape
> >heads... maybe that'll work if I can find it.
> Almost certainly will "work". Those things usually have small
> area effect. You need to get large areas of the disc.
> Possibly just enough demagnetization to affect sector 1 of
> track 0 head 0 is enough.

yeah. no luck finding that thing. oh well. its fun anyway. 


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