the notch is for the key'd connectors, many of the older floppy cables aren't keyed, and relied on your knowledge of pin one being on the same side of the power connector. many of the floppy drives have a little tab that can be "busted off" to enable you to use the newer(late 80's) floppy cables, if it doesn't have one, either get a different floppy drive, get a different cable that isn't tabbed(good luck finding one), or very very carefully force the cable you have onto the floppy drive(sometimes you can take a hobby knive to the cables end and wittle the key'd tab off to make it fit without having to force it the correct way.) also make sure the twist in the cable is closest to the floppy drive and not closest to the mobo, this too will cause problems as the pin out isn't strait through and will reverse the wrong id pins of the cable.