Post #1581447
2026-04-18 08:42 UTC
@RueNahcMohr @muddle @infosecdj
The vast majority of floppy drives use constant motor speed and constant bit rate, on a given disk, so have higher FCPI near the center.
Apple, Commodore, and Sirius were notable exceptions. Apple and Sirius/Victor varied motor speed but kept data rate constant. Commodore kept motor speed constant but varied data rate.
Even at constant rotation rate and data rate, high data densities require a PLL, and thus a VCO or digital equivalent, for reliable reading.
Replies (1)
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@brouhaha@mastodon.social 2026-04-18 09:31
@RueNahcMohr @muddle @infosecdj Apple's earliest 5¼" floppy drives, for the Apple II and Apple III, did not vary the motor speed. Apple started that with the 5¼" Twiggy drive on the Lisa 1, and then on 3½" Lisa and Mac drives. Apple, Commodore, and Sirius/Victor also used Group Coded Recording, rather than industry-standard MFM.