FireWire, developed by Apple Computer's, know also by it's standard, IEEE 1394, is a High Performance Serial Bus, for connecting up to 63 devices via single plug-and-socket connection with data transfer speeds up to 400 Mbps (megabits per second).IEEE 1394 replaced parallel SCSI in many applications. FireWire is also known as i.LINK by Sony's and it uses a different type of cable
Firewire Connectors
A 9-pin FireWire 800 connector
FireWire supports DMA and memory-mapped devices, allowing data transfers to happen without loading the host CPU with interrupts and buffer-copy operations. In comparision to USB which requires the presence of a bus master, typically a PC, which connects point to point with the USB slave. To connect multiple USB devices to a single USB port requires the use of an external intelligent hub. Firewire allows many devices to be connected to a single Firewire hub where the devices can communicate peer-to-peer or with a PC host.
The 1394 standard provides for greater data transfer speeds and the ability to send memory addresses as well as data through a serial port.
The 1995 IEEE 1394 specification that is equivalent to FireWire 400 allows 1,023 buses, each supporting 63 devices, to be bridged together. This networkable architecture supports over 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. Star and tree topologies can be formed, as long as no two devices are separated by more than 16 hops. 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. Through an internal hub, a single end device can use two IEEE 1394 ports to connect to two different devices, creating a daisy-chained pathway that allows the other two devices to communicate with one another as well. The device in the middle affords a physical pathway between the other two devices but is not otherwise involved in their communication with one another.
Firewire's first iteration, now known as FireWire 400, has a maximum data throughput of 400Mbps in half duplex. The next iteration, FireWire 800 (specified under IEEE 1394b), has a maximum data throughput of 800Mbps and works in full duplex. FireWire 400 carries data over a maximum cable length of 4.5 meters with a maximum of 63 devices connected to each interface on the computer. Using new beta connectors and associated cabling, including a fiber-optic solution, FireWire 800 extends to 100 meters. IEEE 1394c allows FireWire over the same Category 5e infrastructure that supports Ethernet, including the use of RJ-45 connectors. It has not been widely supported yet.
Wikipedia reports that Implementation of IEEE 1394 is said to require use of 261 issued international patents held by 10 corporations. Use of these patents requires licensing; use without license generally constitutes patent infringement. Companies holding IEEE 1394 IP formed a license administrator (“patent pool“) MPEG LA, LLC, to whom they licensed patents. MPEG LA sublicenses these patents to providers of equipment implementing IEEE 1394. Under the typical patent pool license, a royalty of US$0.25 per unit is payable by the manufacturer upon the manufacture of each 1394 finished product; no royalties are payable by users.