The __ interface is about two things, if nothing else: speed and efficiency. Its first iteration, now known as __, has a maximum data throughput of 400Mbps in half duplex. Although the numbers imply that USB 2.0 at 480Mbps might outperform __ , the truth is that __ allows a closer saturation of the bandwidth by its devices due to its different encoding mechanism. USB devices are lucky to achieve half of their buss rated bandwidth during sustained operation. Another difference between the two technologies is the amount of power accessible to __ devices. Whereas USB provides less than an ampere of current at 5VDC, F__ specifications allow for the provision of 1.5A at up to 30VDC (and slightly more in some implementations). This production of 45W of power allows for larger devices to be powered by the __ interface, obviating the need for separate external power. FireWire 400 allows 1023 buses, each supporting 63 devices, to be bridged together. This networkable architecture supports more than 64,000 interconnected devices that can communicate directly with one another instead of communicating through a host computer the way USB is required to do. A hop can be thought of as a link between any two end devices, repeaters, or bridges, resulting in a total maximum distance between devices of 72 meters.
IEEE 1394 (FireWire 400)