I keep hearing "theoretical speed" applied to USB, as if there's some theory under which one would be able to get 480 Mb of data transferred in one second. No,

I keep hearing "theoretical speed" applied to USB, as if there's some theory under which one would be able to get 480 Mb of data transferred in one second. No, 480M is the baud. (Download the USB 2.0 spec and check out the wire protocol.) The fastest you can transfer data is with a bulk transfer, which top out at 53248000 Bps = 406.25 Mbps. (That's what I would call the "theoretical speed".) Other transfer types are slower. Companies like advertising "480 Mbps" because it's a high number, but it's not physically possible to transfer data over USB2 that fast.