Floppy Data Capacity

["Joel" <joelbuckley54.nospam.@hotmail.com>]

Here is a comparison of floppy data capacity, historically speaking.
IIRC:
This is by memory, so I may have errors like # sectors vs tracks in 3.5 HD,
but I'm pretty sure of the total capacities.
Also, Apple 3.5 had variable sectors/track, average was 10.

spt - sectors/track
bps - bytes per sector
tpd - tracks per disk
s - sides (or heads)
cap - capacity (bytes) and kilobytes

format coding spt bps tpd s cap cap (k)
standard 4+4 8 256 35 1 71680 70
Apple DOS 3.2 5+3 13 256 35 1 116480 113.75
Apple DOS 3.3 6+2 16 256 35 1 143360 140
Apple 40 trk (non-std) 6+2 16 256 40 1 163840 160
Apple SSDD3.5 DD 10 512 80 1 409600 400
Apple DSDD3.5 DD 10 512 80 2 819200 800
Apple DSHD3.5 HD 18 512 80 2 1474560 1440

SSSD5.25 4+4 8 256 35 1 71680 70
SSSD5.25 4+4 8 256 40 1 81920 80
DSHD5.25 HD 32 256 80 2 1310720 1280
SSSD5.25 4+4 9 256 40 1 92160 90
DSSD5.25 4+4 8 256 40 2 163840 160
DSSD5.25 4+4 9 256 40 2 184320 180
SSDD3.5 DD 9 512 80 1 368640 360
DSDD3.5 DD 9 512 80 2 737280 720
DSHD3.5 HD 18 512 80 2 1474560 1440
DSXD3.5 XD 36 512 80 2 2949120 2880

At its introduction, Apple's 13-sector format added almost 60% capacity over
the industry standard.
The 16-sector upgrade made it almost double. Impressive, for a while.
Alas, while the rest of the industry went 40 tracks, double-sided, double
and high density, Apple stood still.
Also, by doing so much disk control in software, with critical timing, (as
well as integrated video circuitry), you couldn't easily upgrade system
performance by simply putting in a faster processor.
IBM drives became fast and cheap with higher capacity, Apples remained slow
and expensive and low capacity.

With the 3.5 drives, Apple non-standard format added a more modest 25%
capacity.
But once again they fell behind when the industry went to high density.

Lack of intercompatibility made file transfers between the two groups a pain
in the butt.
I believe that it should be possible to read and write SSSD5.25 disks (80k)
with Apple II disk drives.
This format was mainly used by some CP/M computers of that time.
But it was also supported in early versions of PC-DOS/MS-DOS.

I started work on such a project 20 years ago but never finished it.

Sort of like my 384 vertical-line, interlace scan project for the ][+ and
//e.
I'm pretty sure I still have the working prototype for that somewhere in the
basement.
It was a simple design, and worked well but never got around to putting it
into production.