[Info-vax] OT: For MAC Lovers Only :-)

[John E. Malmberg]

On 10/16/2012 3:40 PM, JF Mezei wrote:
> On 12-10-16 15:51, glen herrmannsfeldt wrote:
>
>> The drives convert transitions (0 to 1 or 1 to 0) into magnetic
>> flux reversals, and the opposite on read. (At least for the
>> usual floppy drives and ST506 style hard drives.) All the
>> timing is done by the controller, including precompensation.
>
> But surely the controller would have come from Sony ?

I do not know about the Mac's, but the Apple ][ did not use a disk 
controller chip, they used discrete logic.

That is why the format is so different than anything that uses a 
standard floppy controller.

>> No, the "read track" command, at least for the WD controllers,
>> isn't that useful. You don't know where the sectors start!
>> It might be useful for some debugging problems, or for some
>> damaged media cases.

The read track would have been an attempt to see if any data at all 
could be read off of the floppy disk.

With the read track, you just get a bunch of bits loaded into memory.  I 
do not know if you can even expect them to be all in the right bytes.  I 
last read about this stuff well over 20 years ago.

 From what Glen wrote previously, there is no reason to expect it to work.

Regards,
-John
wb8tyw at qsl.network
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