Double-density (DD) 40-track drives¹². Of 5.25" drives, so the issues are the same for both types. 3.5" drives are essentially smaller versions Refering to common western IBM PC-compatible computers.Īmongst commonly used floppy drives, there are only three basic types by FDFORMAT or 2M) can introduce compatibility problems too, and they should generally be avoided for transfer between systems (unless you also transfer the drive that formatted the disks).īelow I don't discuss the issue of single-sided versus double-sidedĭrives since it seems sufficiently obvious. Using non-standard formats in PCs (as produced e.g. 
stick to “standard” formats if you want to exchange data - 720K for DSDD, 1.44M for DSHD.Įxchanging data with non-PC systems can be more complex (especially with Macs and Amigas), and in such scenarios it’s often better to stick to PC formats for data transfer. always clear data in the lowest-density system the simplest approach here is to reformat disks before any re-use (deleting or overwriting files). always format floppies in the system they’re intended for - thus, if you want to transfer data to a DD-only system, format the floppy in that system, and write to it using whatever system you’re transferring from. ideally, use appropriate media - in particular, use DSDD floppies in DD-only systems. The basic rules of thumb for 3.5” drives are: Problems can also arise when overwriting data on a DD-formatted floppy using an HD drive it’s always better to “write from blank”. Problems arise when using a DSHD floppy in a DD drive: it is possible to format a DSHD floppy using a DD format, but if the floppy was ever formatted with an HD format (or was pre-formatted, as was common in the late 90s), a DD drive won’t be able to correctly reformat it (because its write signal isn’t strong enough). HD drives can adjust their field strength to write appropriately, so an HD drive can write to a DD floppy without creating issues. DSDD and DSHD floppies use different metals, with different coercivities. The main concern with non-LS 3.5” floppies is the metal used in the medium. SuperDisk drives can be ignored as far as backwards-compatibility is concerned: they have two head assemblies, one for “standard” formats, the other for LS formats, and the “standard” head is equivalent to a high-density 3.5” drive’s. 
I’ll limit my answer to common 3.5” formats on PCs, DSDD, DSHD, and SuperDisk, as listed in your question.
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