Re: Disk II Phase Question

[mjmahon@aol.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/