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
weasel@rieska.oulu.fi (Kari Salmela) (06/23/91)
< Talk about punching a hole in the 3.5" DD disk >
.. And if you happened to format a DD disk in a Compaq Portable III with
no special parameters, only way to recover some information from the disk
with another computer is to punch new hole in the disk. Neat :)
--- Kari Salmela (weasel@rieska.oulu.fi) Virkakatu 8 E 18 90570 Oulu
--- LuTK / TOL (dpt. of information processing science) at U of Oulu.
------------------------------------------------------------------------
" Hackers unite. "ntaib@silver.ucs.indiana.edu (Nur Iskandar Taib) (06/23/91)
>.. And if you happened to format a DD disk in a Compaq Portable III with >no special parameters, only way to recover some information from the disk >with another computer is to punch new hole in the disk. Neat :) Naah... just take it to the nearest IBM PS/2 - they have the same problem. In fact I'm surprised to hear that Compaq doesn't put autosensing drives in its computers either.. Darn! Why is it that the most expensive of PCs don't have autosensing drives? -- ------------------------------------------------------------------------------- Iskandar Taib | The only thing worse than Peach ala Internet: NTAIB@AQUA.UCS.INDIANA.EDU | Frog is Frog ala Peach Bitnet: NTAIB@IUBACS ! -------------------------------------------------------------------------------