Re: Disk II Phase Question

["Jplcsch" <jplcsch@wanadoo.fr>]

<mjmahon@aol.com> wrote in message
1105732032.041520.31230@c13g2000cwb.googlegroups.com">news:1105732032.041520.31230@c13g2000cwb.googlegroups.com...
> Bryan Parkoff wrote:
> > Jplcsch,
> >
> >     Do you mean that head contains a "BIT" scanner which it is wider
> than
> > normal "BIT" scanner?  It looks like it reads and write each 1 1/2
> track
> > instead of 1 track.  You receive valid data from full track while you
> ignore
> > invalid data from half track at the same time.  Is it correct?
>
> It's simple.  The amount that the head moves radially for one step
> is less than the radial width of the head (the width of the track that
> it reads or writes).
>
> This could be viewed as "overkill" on the resolution of the stepper
> motor,
> or as using a wider head than necessary.  In fact, the signal-to-noise
> ratio of the read signal, and therefore its reliability, is a function
> of
> the track width, and the early media could be quite non-uniform or
> noisy,
> so the use of the "single density" head width was appropriate.
>
> -michael
>
> Parallel computing for a network of 8-bit Apple II's!
> Home page:  http://members.aol.com/MJMahon/
>

As every time  explications from Michael are perfects !