Windows 95’s floppy detector got opposite answers from two kinds of drive
A no-spin trick could detect a disk, but its result meant the opposite thing after a drive swap.
A one could mean a disk was in the drive. On another drive, the same one meant the slot was empty. Both drives could answer consistently and still leave Windows guessing.
In his follow-up about Windows 95’s abandoned insertion detector, Raymond Chen describes two drive styles. A special command sequence returned opposite presence values between them. The missing piece was identifying which style the computer had.
Training the detector after the first real floppy operation created a different problem. A new owner could insert a game disk, expect something to happen and see nothing. Later, after an unrelated disk operation established the drive’s style, the same action might work.
Chen writes, “Human beings value predictability.” A feature that woke up after apparently unrelated activity would teach the opposite lesson.
Hardware replacement made calibration worse. Classic floppy drives were not Plug and Play, so the OS had no reliable notice that someone had swapped one style for the other. Yesterday’s learned meaning could become exactly wrong after a repair.
The no-spin check also relied on behavior outside the specification’s original purpose. Chen says the cost was large beside the limited benefit, including an unwanted drive spin-up when a disk was inserted.
A silent hardware swap still makes a good test for any modern feature that remembers what a device used to mean. The failure may arrive long after the detector earned its first clean result.