Re: Apple2 disk controller questions

[Rubywand <rubywand@swbell.net>]

Fabrice Frances writes ...
> 
> Hello all, I'm not familiar with the Apple][ so I was wondering why there
> seems
> to be 6656 bytes read per floppy rotation instead of 6400.
> (I'm used to MFM disks running at 300tr/min and with a 250kbps rate, this
> means 6400 bytes per track)
> - Apple][ disks are FM encoded, right ?
> - which of the following is wrong for Apple][ drives: rotational speed of
> 300tr/min,
> or transfer rate of 250kbps ?
 ....


     Apple II 5.25" diskettes are GCR encoded. Rotation speed is 300rpm
(200ms per rotation). 250kbps sounds about right for the max transfer rate--
not sure about that, though.

     A good source of information about Apple II 5.25" disk encoding and
layout is Beneath Apple DOS by Worth and Lechner.



Rubywand