> On 2020-10-21, at 10:55, Francesco Messineo <francesco.messineo_at_gmail.com> wrote: > >>> there's no "QD" magnetic media, SD/DD/QD magnetic media was always the >>> same (300 oersted). >> >> Right, but AFAIU that's not the point >> >>> Probably the diskettes sold as QD/96 tpi were just higher quality. >> >> Delivering higher resolution without changing the magnetisation characteristics. Similar to "Type I" in analogue audio tapes. One used the same oersteds/bias/eq for different tapes of the same "Type I" but the results could be _hugely_ different between different tapes. > > in the case of floppy disk drives, it was a better (smaller) head > design and a much better head positioning stepper and mechanics. The > design of 96tpi and 100tpi drives started by using the old available > magnetic media. Then after that, floppy disk manufacturers thought > they would make more money if they advertised their standard media as > "QD" and 96tpi certified. As they already did the same then MFM and > double density was introduced, with always the same magnetic media > that was used with FM modulation (called single density). > I still have boxes of very old floppies sold as single density. > I would not compare analog cassettes to floppy disks. Why not? It's the very same idea and principle. You could have magnetic medium that was not able to record enough density (higher frequencies) and you could have another one which was. Both having the same magnetisation parameters. The same here - you can have a medium, which is capable of recording higher frequency (density) and you can have one, which is not. Heads and co. play an important role too, which – BTW – applies to analogue tapes as much as it does for disks, but the underlying principle is the very same in both cases. Also, I don't say that what you assert about vendors making money with marketing buzzwords is incorrect. It most probably is. What I object to, is that you _directly_ link the magnetic characteristic (300 oersted) with with the achievable resolution (density). This is neither true for disks nor for tapes. For the very same reasons in both cases - something you called "quality". What it should be with "QD" floppies is that they should be tested and certified to be capable of delivering higher resolution. That doesn't mean that "DD" medium is automatically not. It's just that it wasn't certified for that. How it was in reality - I don't know but I can imagine the vendors slapping the marks at will while being relatively sure that nobody will sue them if _some_ of those media do not perform. -- SD!Received on 2020-10-21 12:00:03
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