Date   : Tue, 23 Mar 2010 09:19:25 +0100
From   : anders.carlsson@... (Anders Carlsson)
Subject: Re-using floppies

Rick Murray wrote:
> the HD head is narrower than the DD

Pete Turnbull wrote:
> No, they are exactly the same width.

I believe you both are correct, depending on the context. A 5.25" floppy 
disk is either 40 or 80 tracks (give or take those 35 and 77 track formats) 
and in this case there may occur inconsistencies if writing a 40 track 
floppy disk on a 80 track (1.2 MB) drive. However a 3.5" floppy disk is 
always (?) 80 tracks, only varying density and magnetic strength so in this 
case the head on a 1.44 MB (HD) drive should not be more narrow than the one 
on a 720K (DD) one. The difference in coercivity between 3.5" DD and HD is 
smaller than it is for 5.25" DD/HD, which means you might get away with 
formatting and using 3.5" disks of the wrong type but usually fail terribly 
if you try to use a 5.25" HD floppy disk on a DD system.

Best regards

-- 
Anders Carlsson