RE: CBM 8280

From: William Levak (wlevak_at_cyberspace.org)
Date: 1999-09-08 00:25:38

On Mon, 6 Sep 1999, Steve Judd wrote:

> Hi Bill,
> 
> On Fri, 3 Sep 1999, William Levak wrote:
> 
> > HD disks use a magnetic particle that requires a higher electic field to
> > write them.  In addition, the write head is narrower.  If you use a SD,
> > DD, or QD disk in a HD drive, the higher electric field will cause the
> > signal to be spread over adjacent tracks.  If you format a DD disk to a DD
> > capacity in a HD drive, then you will be able to read and write it because
> > of the greater spacing between tracks.  You will, however, only be able to
> > use it in a HD drive because the main signal is too narraw to be read
> > reliably by a DD drive.
> 
> This seems backwards to me, and runs counter to my experience.  I would
> think that the lower current of a DD head would mean that sometimes the
> HD head has a problem reading it.

The two situations are different.  The read heads on a HD drive are
sufficiently sensitive to read DD disks.  The problem comes in writing.

Also 5.25 drives are different than 3.5 drives.  HD 3.5 drives have a
density select line that selects between writing in DD or HD mode.
5.25 drives do not have this.

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