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Was ED media a lie?

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Alex Eisenhut:
Floppy disks came in various densities like SD, DD, HD, then ED. Extended density apparently used perpendicular recording which requires a magnetic "return" layer in the media to work, unlike previous densities which were longitudinal recording.

You'd think that's not interchangeable, and writing in ED mode to HD media shouldn't work.

But there are people claiming they just punch a hole in a HD disk to fool a ED drive into recognizing an ED disk, and it works.

How is this possible?

Phil1977:
It works just as most other forms of tuning or overclocking.

OEMs engineer their products with lots of safety margins so that the product should live for a specified time in a wide range of possible environments.

Tuners/Tweakers take these margins to make the product work once under a certain set of conditions.

Probably it´s the same with these floppy disks. Probably the required magnetic resolution of the ED-drive is somewhere near the average-resolution of HD-media. And the average magnetic resolution of specified ED-media is that much higher that always exceeds the requirement.

Alex Eisenhut:
Sure but how is the flux getting back to the head? Is it just tunneling its way in the HD layer without disturbing the domains too much?
And if so, why bother making a new formulation and media?
https://extrapages.de/archives/20190102-Floppy-notes.html

People have been formatting, or trying, across various densities and it never holds long-term, but this ED stuff looks like it shouldn't even format at all.
Like when trying to format a HD disk on a DD drive, at least in the 5.25" world, it fails pretty quick.
I'd guess the ED trick wouldn't hold data that long. Who knows.

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