Re: Anybody aware of the description of a 19pin connector of an Apple 5.25 Disk Drive ?

[Michael J. Mahon <mjmahon@aol.com>]

Peter Dassow <z80eu@arcor.de> wrote:
> On 06.05.2013 03:11, Michael J. Mahon wrote:
> 
>> 
>> I thought you were confused about the level difference between PC floppy
>> drives and Apple floppy drives--and you are.
>> 
>> No "cable" can convert the Apple floppy interface to a standard floppy
>> interface.
>> 
>> In 1982, I converted two standard SA400's to be Disk ][ compatible. It
>> involved about six pages (single-spaced) of wiring changes to the
>> digital/analog board in the drive. I recall spending about three hours
>> modifying each board--lots of wire and solder!
>> 
>> The net effect of the extensive modifications was to disable virtually all
>> of the digital controller on the board, directly exposing the head stepper
>> motor phases and directly connecting to the write signal and the detected
>> head read signal.
>> 
>> Since the SA400 boards were built entirely of MSI TTL chips, all nodes of
>> the circuit were available for modification. Modern (!) floppy drives have
>> many fewer chips with higher integration levels, so it is unlikely that
>> such a modification would still be possible.
>> 
>> -michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
>> 
> 
> Ok, I got it, regardless of the fact that I really owned non-Apple Floppy
> Disk Drives around 1985. May be these non-Apple Drives were still
> compatible to these original ones, I can't check this now.
> But this is almost unbelievable that nobody yet created a logic board
> with an FPGA/whatever which converts the signals/creates the missing
> signals. May be too much old drives are still available ...

Yes, there were countless third-party Disk ][ compatible
drives--full-height and half-height. All had standard mechanisms and
distinctly non-standard electronics. They all had 20-pin ribbon cables, not
34. 

And there is no way that a standard drive with standard controls can be
made to do the fractional track tricks that can be done with a Disk ][
compatible drive. 

Although it is relatively easy to use an "adapter" to raise the semantic
level of an interface, it is not generally possible to use an adapter to
*lower* the level of an interface. When you add in the real-time nature of
the Disk ][ interface, it's game over. 

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon