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

[glen herrmannsfeldt]

JF Mezei <jfmezei.spamnot at vaxination.ca> wrote:
> On 12-10-16 08:12, John E. Malmberg wrote:

>> It may be possible to use the "read track" low level floppy disk 
>> controller command, which basically just copies all the bits read into a 
>> memory buffer and then use a program to try to separate the data.

> Isn't that what backup/physical does ?

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.

> Note that with the Macintosh, Apple used Sony drives. Sony developped
> that 3.5" hard floppy disk and Apple was first to use it. It did become
> industry standard.

I am not sure by now that Apple was first to use it, but at least
first to popularize it. The format is pretty much the same as
the Apple II format.

> Not sure if the "low level" format could have been Mac 
> Proprietary since that would be done by the device, wouldn't it ?

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.

There are SCSI and IDE floppy drives, which include all 
the controller logic within the drive.

-- glen