... But NEC beat IBM by already doing 'five blades' in 1988 selling PC-88 VA3 with 'Triple' or '2TD' format 3.5" floppy sporting 13MB unformatted 9MB formatted capacity. Same perpendicular head as ED, same magnetic medium, same bitrate, 3 times more tracks (240) while still using cheap stepper motor unlike ZIP head actuators, compatible with same standard ED floppy controller chips. Sadly no one in the west adopted it :(((
There was one more avenue for bumping capacity never really explored on PC - zone bit recording invented by Chuck Peddle in 1961 and supported by Floppy controllers in Macintoshes, Commodore (Chuck Peddle designed drives) and Victor 9000 (Chuck Peddle designed whole computer). Free 50% capacity bump. Victor 9000 pulled 1.2MB capacity out of Double Density 80 track 5 1/4 drive.
Combine 2TD wiht ZBR and we could have had cheap 13.5MB formatted capacity floppies since 1988.