Despite the punchline, the USB floppy spec is actually incredibly restrictive and only supports 720K, 1.25MB and 1.44MB formatted capacities. This means, ironically for a spec partially written by a friend of Raymond Chen's, that you can't read the Microsoft 1.68MB DMF floppies used for software distribution with a USB floppy, but it also means that it's impossible to support the older 400K and 800K Mac formats. To be fair, those formats also require a special drive mechanism (the disk spins at different rates depending on which track you're reading), but there's no way to expose them within the USB floppy spec. There's an entirely justifiable argument for manufacturing a separate Mac drive with different functionality and requiring its own drivers.<p>(Edit to fix capacity)