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

On Wed, May 03, 2006 at 12:34:59PM -0500, Mike McCarty wrote:
> Andrew Sackville-West wrote:
> >On Wed, May 03, 2006 at 11:29:31AM -0500, Mike McCarty wrote:
> >
> >>Andrew Sackville-West wrote:
> >>
> >>>On Wed, May 03, 2006 at 10:24:00AM -0500, Mike McCarty wrote:
> >>>
> [snip]
> >>No, a sector copy is not a bit-for-bit copy, as sectors do not have
> >>to be arranged sequentially on the track. In fact, sectors used
> >>normally to be written with interleave to speed up access. I haven't
> >>looked into it lately, so I dunno whether sectors are now commonly
> >>written with interleave of 3 as used to be, or are now sequential.
> >
> >
> >yup. I only mean that Im interpreting the statements in the install
> >guide as indicating that the entire disk image, boot record and all is
> Ok. But it is important sometimes to make these distinctions.
> A sector-by-sector copy is not a bit-for-bit copy, as floppies
> do not store bits. There are inter-sector gaps, for example.

fair enough. 

> >being copied. I might have some truly blank floppies around... I'll
> >play with them and see what happens.
> 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. 

> 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
tried so far:

big magnet on a 15" speaker
microwave (he he)
ac motor on my drill press
various fridge magnets wiped over the surface
holding on my monitor while degaussing the monitor


somewhere around here I have a degausser for cassette tape
heads... maybe that'll work if I can find it.


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