I'm sort of curious what design changes Apple made to the "Universal" A9M0106 drive to resolve the compatibility issue with the bugged ROM, as that drive will boot a 64K ROM Mac without doing the little dance-of-joy. (I have both styles of 800k drive to go with my 512k now, and can confirm that the later drive will indeed work to boot an old System 2.0 disk directly without the HD20 init.)