FireWire is an I/O interface developed by Apple Computer. It is also known as IEEE 1394, which is the technical name standardized by the IEEE. Other names for IEEE 1394 include Sony i.Link and Yamaha mLAN, but Apple's FireWire name the most commonly used.
There are two primary versions of the FireWire interface – FireWire 400 (IEEE 1394a) and FireWire 800 (IEEE 1394b). FireWire 400 uses a 6-pin connector and supports data transfer rates of up to 400 Mbps. FireWire 800 uses a 9-pin connector and can transfer data at up to 800 Mbps. The FireWire 800 interface, which was introduced on Macintosh computers in 2003, is backwards compatible with FireWire 400 devices using an adapter. Both interfaces support daisy chaining and can provide up to 30 volts of power to connected devices.
FireWire is considered a high-speed interface, and therefore can be used for connecting peripheral devices that require fast data transfer speeds. Examples include external hard drives, video cameras, and audio interfaces. On Macintosh computers, FireWire can be used to boot a computer in target disk mode, which allows the hard drive to show up as an external drive on another computer. Mac OS X also supports networking two computers via a FireWire cable.
While FireWire has never been as popular as USB, it has remained a popular choice for audio and video professionals. Since FireWire supports speeds up to 800 Mbps, it is faster than USB 2.0, which maxes out at 480 Mbps. In fact, even FireWire 400 provides faster sustained read and write speeds than USB 2.0, which is important for recording audio and video in real-time. Future versions of IEEE 1394, such as FireWire 1600 and 3200, were designed to support even faster data transfer speeds. However, the FireWire interface has been superseded by Thunderbolt, which can transfer data at up to 10,000 Mbps (10 Gbps) and is backwards compatible with multiple interfaces.