As mentioned in the Types of MO Media section, MO drives can use several different capacities of disk. Current 640MB 3½" drives can read and write 128MB, 230MB, 540MB and 640MB disks. (Early 640MB drives could not write to 128MB disks.)

Since there is currently no special MO driver software for the Amiga, it is not possible to access different capacity MO disks using the same device name (but see Mounting and Using the Drive and Disks).

On my Amiga, I mount the MO0: device to access 640MB MO disks. To access 128MB, 230MB or 540MB media, I would have to create other mount files, e.g. for devices MO128:, MO230: and MO540:, in order to access disks of these capacities. This is not a major problem, since you will probably mostly use disks of the highest capacity your drive can handle. See the example mount files.