USB compared with FireWire
USB was originally seen as a complement to FireWire (IEEE 1394), which was designed as a high-speed serial bus which could efficiently interconnect peripherals such as hard disks, audio interfaces, and video equipment. USB originally operated at a far lower data rate and used much simpler hardware, and was suitable for small peripherals such as keyboards and mice.
The most significant technical differences between FireWire and USB include the following:
USB networks use a tiered-star topology, while FireWire networks use a repeater-based topology.
USB uses a "speak-when-spoken-to" protocol; peripherals cannot communicate with the host unless the host specifically requests communication. A FireWire device can communicate with any other node at any time, subject to network conditions.
A USB network relies on a single host at the top of the tree to control the network. In a FireWire network, any capable node can control the network.
USB runs with a 5 V power line, whereas Firewire can supply up to 30 V.
These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, in real-world use, especially for high-bandwidth use such as external hard-drives, FireWire 400 generally, but not always, has a significantly higher throughput than USB 2.0 Hi-Speed.[18][19][20][21] The newer FireWire 800 standard is twice as fast as FireWire 400 and outperforms USB 2.0 Hi-Speed both theoretically and practically.[22] The chipset and drivers used to implement USB and Firewire have a crucial impact on how much of bandwidth prescribed by the specification is achieved in the real world, along with compatibility with peripherals.[23] Audio peripherals in particular are affected by the USB driver implementation.[24]
One reason USB supplanted FireWire, and became far more widespread, is cost; FireWire is more expensive to implement, producing more expensive hardware.
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