Re: Disk II Phase Question

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

Hello,

> The Disk II has a nominal rotation speed of 300 rpm; that causes one
> revolution every 200 msec. The nominal read pulse spacing is 4
> microseconds. That means approximately 50,000 bits in one revolution of
> the disk.
    I understand now.  The reason is that I say ($5F00) 24,320 bytes or 
194,560 bits per track.  It is what it is found in Copy II Plus' Nibble 
Anaylzer.  I assume that it should be 6,576 bytes for valid data including 
address header and data header and 6-2 data per track.  I will study more.
    Thank you very much for the information.

Bryan Parkoff

>
> Not all of these are used for data, because extra bits must be used for
> the self-synchronizing bytes, in addition to allowance for "slop" when
> sectors are written. Also, the standard formats must allow for the
> possibility of faster drives (1% drive speed variation causes +/-500
> bits in this nominal track length).
>
> Disk recording is an analog medium. It does not easily accomodate exact
> precision.
>