Floppy Disc Capacities [was Pictures of My Machine Room (So Far)]

[Chuck Guzis]

On 20 Jun 2007 at 22:01, Jim Leonard wrote:


> I didn't explain myself well.  I used to format high-quality diskettes 
> in the early 1990s as 21-sector instead of 18, and I consistently saw 
> errors after about a year of storage on the inner tracks (and never on 
> the outer tracks).  I wasn't speaking from a storage standpoint, but 
> rather from a reliability standpoint.

You'd have likely seen nearly the same errors if you'd formatted the 
floppies as 18 sectors.  The issues of reliability come in when 
writing, not reading.  21 sectors gives you something like an 8-byte 
gap (i'll calculate it if you want).  8 bytes is .00064 of a track, 
so if your spindle speed is too fast, you can easily overwrite the 
gap.

But as far as bit-packing density goes, 18 and 21 sectors are the 
same.

I would submit that by the early 1990's, there weren't any high-
quality DSHD diskettes.  DSED were even worse.

Cheers,
Chuck