Re: Disk II Half - Quarter Tracks

["mmphosis" <markstock@mail.com>]

On Feb 8, 7:24 pm, "Bryan Parkoff" <nos...@nospam.com> wrote:
>     Can you write the bit stream?  Like this AA AB 96 96 96 .... 96 96 96 FC
> FC on Track 1 without address field and data field.  AA AB is the start of
> bit stream.  FC FC is the end of the bit stream.  Try to read all bytes on
> Track 1 and use loop to count the number of byte value 96.
>     Try to write by replacing from 96 to 97 on Track 1.25.  9A on Track
> 1.50.  9B on Track 1.75 and 9C on Track 2.  Did it tell you when you attempt
> to read and count the byte values on Track 1, Track 1.25, and Track 1.50.
> Did Track 1, Track 1.25, and Track 1.50 report to be 9A?  Did Track 1.75
> report 9B?
>     It is evident that Track 1.50 has overwritten 9A to replace 96 and 97 on
> Track 1 and Track 1.25 because the arm head is too width.  Track 1.75 and
> Track 2 are not overwritten.
>     Did you have done your experiment?
>
> Bryan Parkoff

Ah, copy protection schemes.  Use different nybbles.  Write just a
little bit of data on a quarter track.  Yup, you are right, it
overwrites because the head is too wide.  It looks like the same data
on other quarter tracks.  Half tracks.  3/4 tracks.  Writing data in
spirals on the disk.  Adjust the stepper motor timing, ever so
slightly.  Write to the 36th track: tracks 34.25, 34.5, 34.75, 35.
Remove the magnetic coating from the disk on certain tracks, but
require that the disk be written to on other tracks.  Enter the text
from the long speech on page 34 of the manual to continue.  Utter
madness.