On Fri, 8 Sep 2023, Liam Proven via cctalk wrote:
Everything I know about floppy disks
2023-08-28
Floppy disk drives are curious things. We know them as the slots that ingest
those small almost-square plastic "floppy disks" and we only really see them
now in Computer Museums. But there's a lot going on in that humble square of
plastic and I wanted to write down what I've learned so far.
https://thejpster.org.uk/blog/blog-2023-08-28/
It's got some really good stuff, but some things that are awkward,
although few totally WRONG.
For example, he says that 8" drives have 40 tracks. It's 77, and that
becomes important.
He mentions that 100tpi drives are 77 track, but doesn't mention WHY they
aren't 80.
He says that 1.2M drives are 360 RPM, but mis-states that as being to
compensate for inadequacy of the media, rather than that it was to match
8"
He gets the track width right as the reason why 1.2M drives are bad at
writing 40 track disks, but erroneously thinks that the coercivity of the
HD disk is a reason. (1.2M drives handle both 300 and 600 Oersted disks)
He correctly explains "quad density" drives, but doesn't implicate
marketing for the ambiguous naming.
I don't care for his explanation of MFM.
"If you programmed the controller to run at 250 kbit/sec on a 360 rpm
drive, the end of the track would crash into the start of the track and
the data would be corrupted." could more correctly say that the track is
too short and would overlap, not "crash into".
His table of disk formats is somewhat sparse, and on PC fails to note the
importance of minor version number of DOS (720K was dos 3.20; 1.4M was DOS
3.30).
He does an excellent job of explaining why a "1.44MB" disk is 1.4M, NOT
1.44M.
Overall, a good start, for MOST aspects.
--
Grumpy Ol' Fred [email protected]
