Charlie wrote:
> "Steven Hirsch"  wrote in message 
> news:1p6dnXqfLPZZdhXUnZ2dnUVZ_jOdnZ2d{at}giganews.com...
>> Charlie wrote:
>>> "Steven Hirsch"  wrote in message 
>>> news:YdKdnWEBU6Dx5RXUnZ2dnUVZ_h2WnZ2d{at}giganews.com...
>>>> Alex Freed wrote:
>>>>> sicklittlemonkey wrote:
>>>>>> Are you talking about reading actual Apple II
disks, a la FDI etc, or
>>>>>> just reading and writing to modern HD media via an
emulation of 5.25 &
>>>>>> 3.5 GCR formats?
>>>>> After posting I remembered that the Apple 3.5"
disks were "special".
>>>>> AFAIK they use variable speed to using a PC drive to
read/write Apple
>>>>> 3.5" disks is at least difficult.
>>>> Wouldn't it be possible to cleverly emulate the variable
speed zones in 
>>>> software by playing with the data rate?  (For some value
of cleverness 
>>>> at any rate).
>>>>
>>>> Steve
>>> Yes, Disk2FDI manages to read Apple 3.5" disks in PC type
(single speed) 
>>> 3.5" drives.
>> I didn't realize that disk2fdi worked with 3.5" drives!
> 
> It also supports 3" drives (whatever they are) and 8"
drives.  I've found 
> when reading 3.5" Apple II disks there is an occasional disk that
won't read 
> in either the upper tracks or the lower tracks.  Using a different 3.5" PC 
> drive usually cures the problem.
> 
>> Another example is the Copy II Plus option board.  Unless I'm confusing it 
>> with something else, it was able to read and duplicate 800K Mac diskettes 
>> (same low-level format, I think).
> 
> I'm not familiar with the Copy II Plus board but another interesting card is 
> the PC Transporter.  It can read/write an Apple II 3.5" drive in
either GCR 
> with the variable speed (800K) or PC MFM with single speed (720K).  In this 
> case though, I don't believe the speed is done in software.  If I remember 
> correctly the PC Transporter somehow keeps the speed from varying in the 
> drive.

PC drives are not even capable of the "zone" speed changes that Apple
3.5" drives do.  To read or write an Apple GCR 3.5" disk with a PC drive
requires changing the bit clock rate.

-michael

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