chris@genly.UUCP (Chris Hind Genly) (06/20/91)
Thanks to all those that sent email anwering my questions about floppies.
Here is a summary:
5 1/4 inch
----------
DS DD, 40 tracks, 9 sectors/track, 360K formatted
DS HD, 80 tracks, , 1.2M formatted, 1.4(?) raw
- Diskette case is identical for the DD and HD diskettes. There is no
hole or slot in the case to distinguish between the two densities.
- Coercivity of HD diskettes is about twice that of DD diskettes.
So a DD drive cannot make enough signal impression on an HD diskette.
- The HD track 0 is about .100" closer to the hub than the DD track 0.
Many HD disks don't have acceptable media where track 0 of a DD diskette
would be.
3 1/2 inch
----------
DS DD 80 tracks, 9 sectors/track, 720K formatted, 1M raw
DS HD 80 tracks, 18 sectors/track, 1.44M formatted, 2M raw
DS ED 2.88M formatted, 4M raw,
requires DOS 5.0 and above.
- DD and HD diskettes have roughly the same coercivities.
- HD diskettes have a square hole in the plastic casing directly opposite
from the write-protect hole. DD diskettes do not.
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----------------------------------------------------------------hartung@crl.ucsd.edu (Jeff Hartung) (06/20/91)
In article <chris.4257@genly.UUCP> chris@genly.UUCP (Chris Hind Genly) writes:
<3 1/2 inch
<----------
<
< DS DD 80 tracks, 9 sectors/track, 720K formatted, 1M raw
< DS HD 80 tracks, 18 sectors/track, 1.44M formatted, 2M raw
< DS ED 2.88M formatted, 4M raw,
< requires DOS 5.0 and above.
<
<- DD and HD diskettes have roughly the same coercivities.
<
<- HD diskettes have a square hole in the plastic casing directly opposite
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
< from the write-protect hole. DD diskettes do not.
...and we all know the trick one can therefore use to format DD 3.5" diskettes
at 1.44 Mb, right? :-) Of course, one must take care not to damage the
diskette when punching the hole into the plastic casing, and I wouldn't
recommend this for anything you don't have a second, more reliable copy of
somewhere (i.e., don't use these for hard disk backups, etc. :-)
--
--Jeff Hartung--
Disclaimer: My opinions only, etc., etc., BLAH! BLAH! BLAH!...
InterNet - hartung@crl.ucsd.edu BITNET - hartung@ucsd
UUCP - ucsd!crl.ucsd.edu!hartungdonm@pnet07.cts.com (Don Maslin) (06/21/91)
> >5 1/4 inch >---------- > [...] >- The HD track 0 is about .100" closer to the hub than the DD track 0. > Many HD disks don't have acceptable media where track 0 of a DD diskette > would be. > If that is so, why doesn't a HD drive get 'confused' when reading a DD diskette? Keeper of the CP/M System Disk | UUCP: {nosc ucsd crash ncr-sd}!pnet07!donm Archives for the Dino(saur)SIG | ARPA: simasd!pnet07!donm@nosc.mil - San Diego Computer Society - | INET: donm@pnet07.cts.com