Re: Disk II Phase Question

["Bryan Parkoff" <nospam@nospam.com>]

Hello,

    Now, I understand how Disk II Drive work.  There is only one unanswered 
question.

    Do each even/odd track have total ($5F00) 24,320 bytes in nibble or 
194,560 bits.

    I suspect that some copy protectioned diskettes do not have DOS 3.3, 
ProDOS, nor general file and directory structure.  They may not have 
sectors, or they may have only two sectors each track.  When one sector is 
read from track 0, it begins to search for tracks before it reads one or two 
sectors.  One or two sectors are loaded into memory.
    It is like audio tape that it does not need file and directory 
structure.  It may be track to track stream or sector to sector stream. 
Sometimes, some people claim to be spiral that does not need file and 
directory structure.
    What do you think?

Bryan Parkoff



"Jplcsch" <jplcsch@wanadoo.fr> wrote in message 
news:41e82c41$0$7108$8fcfb975@news.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 !
>
>
>
>