[Coco] 3.5 in 720K vs 1.4 meg floppy diskettes

[Chris Spry]

I've played around with this quite a bit actually and here is my experience
with this sort of thing:

1.44MB 3.5" Floppy drive acting as a 720k drive.....works great!  I've put
together several dual floppy drives with this configuration and it works
great with DD 720k floppy disks.  My current config at home is this
configuration (/DO is a 360k 5.25" floppy and /D1 is a 1.44MB Floppy).  Have
yet to have a DD 720k disk fail on me (even formatted as 160k in RS-DOS!).

Putting a 1.44MB floppy disk in and formatting it as double or single
density (720k or 160k under RSDOS)....sucks!  Very unreliable.  Most of the
time I start losing data and get I/O errors anywhere from days to weeks
after initiation (on rare occasions hours). Even with the second hole taped
over to trick the drive.

-Chris Spry

----- Original Message ----- 
From: "Marty Goodman" <martygoodman at worldnet.att.net>
To: <rayanddoraleew at earthlink.net>
Cc: "Arthur Flexser" <flexser at fiu.edu>; "CoCo List" <coco at maltedmedia.com>
Sent: Wednesday, December 10, 2003 3:55 PM
Subject: [Coco] 3.5 in 720K vs 1.4 meg floppy diskettes


> It's true that the 1.4 meg 3.5 in floppies have a different (higher)
> magnetic coercivity than the 720K variety.
>
> HOWEVER, the difference between a 3.5 in 720K and a 3.5 in 1.4 meg is not
> all that great... about 16% different, or something like that (I vaguely
> seem to recall the 720's had a coercivity of 600 oersteds, and the 1.4's
had
> a coercivity of 700 oersteds.  This really isn't that big a difference,
and
> it would not surprise me to learn the 1.4 megs will work acceptably in the
> 720K drives (or in a 1.4 meg drive set to act as a 720K drive).
Acceptably
> well, perhaps... but it's not clear the reliablity will be the same, nor
> that the amount of time the data will last on them, when used as low
density
> diskettes, will be the same, either.
>
> With 5.25 in floppy diskettes (remember them?) it's another matter:  The
> 360K "low density" 5.25 in floppies had a magnetic coercivity of 300
> oersteds, if I recall correctly, and the 1.2 meg "high density" 5.25
> floppies had a magnetic coercivity of either 600 or 700 oersteds (I think
it
> was 600).  THAT is an enormous different, and it thus surprise no one that
> the 1.2 meg "high density" floppies CANNOT be written on a CoCo style 360K
> floppy drive.
>
>  ---marty
>
>
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