On Tue, 27 Nov 2001, [iso-8859-1] Hársfalvi Levente wrote:
> Hi!
>
> William Levak wrote:
> >
> > On Mon, 26 Nov 2001, [iso-8859-1] Hársfalvi Levente wrote:
> >
> > > 8x50 ---> IBM 1.2M: mechanically incompatible (100tpi vs. 96tpi), and
> > > logically incompatible (GCR vs. MFM, like above). Even if the PC could
> > > read the non-MFM data stream (like with the Catweasel), the misalignment
> > > would be a hard problem to solve.
> >
> > 8x50 drives are quad density and IBM 1.2M drives are high density. They
> > are nominally the same data density, but the magnetic films are different.
> > The heads require different magnetic field strengths to read and write.
>
> AFAIK SD, DD and QD are about the same in their magnetic parameters.
SD, DD and QD are the same except for the particle size in the magnetic
film.
> 1.2M drives are surely capable of switching between "low" and "high"
> density operating mode (that's why they can still record 360K DD disks).
> With pulling the 'LD line low, the floppy controller can tell the drive
> to change to "low density" mode. (I experimented with this setting and
> found that it's even significant during reading a disk. By setting the
> PC drive onto a halftrack of a Commodore disk, I got a lot more false
> spikes on 'RD when the drive was set to HD mode ( = 'LD was not
> asserted)).
Although a HD drive can read and write a 360K format, it is not
necessarily compatible with that of a DD drive, or at least, not ALWAYS
compatible.
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