FireWire is Apple Computer's name for the IEEE 1394 High Speed Serial Bus. It was initiated by Apple and developed by the IEEE P1394 Working Group, largely driven by contributors from Apple, although major contributions were also made by engineers from Texas Instruments, Sony, Digital Equipment Corporation, IBM, and SGS Thomson (now STMicroelectronics).

Apple intended FireWire to be a serial replacement for the parallel SCSI bus while also providing connectivity for digital audio and video equipment. Apple's development was completed in 1995. As of 2006, IEEE 1394 is currently a composite of three documents: the original IEEE Std. 1394-1995, the IEEE Std. 1394a-2000 amendment, and the IEEE Std. 1394b-2002 amendment (there is a 1394c amendment that provides support for 800 Mbit/sec operation over 100 m of Category 5 unshielded twisted pair cable that will be published soon).

Sony's implementation of the system is known as i.Link, and uses only the four signal pins, discarding the two pins that provide power to the device in favor of a separate power connector on Sony's i.Link products.

The system is commonly used for connection of data storage devices and digital video cameras, but is also popular in industrial systems for machine vision and professional audio systems. It is used instead of the more common USB due to its faster effective speed, higher power-distribution capabilities, and because it does not need a computer host. Perhaps more importantly, FireWire makes full use of all SCSI capabilities and, compared to USB 2.0 High Speed, has higher sustained data transfer rates, a feature especially important for audio and video editors.

However, the small royalty that Apple Computer and other patent holders have initially demanded from users of FireWire (US$0.25 per end-user system) and the more expensive hardware needed to implement it (US$1–$2) has prevented FireWire from displacing USB in low-end mass-market computer peripherals where cost of product is a major constraint.

According to Michael Johas Teener, original chair and editor of the IEEE 1394 standards document, and technical lead for Apple's FireWire team from 1990 until 1996:

FireWire 400 can transfer data between devices at 100, 200, or 400 Mbit/s data rates (the actual transfer rates are 98.304, 196.608, and 393.216 Mbit/s, ie 12.288, 24.576 and 49.152MBytes per second respectively). These different transfer modes are commonly referred to as S100, S200, and S400. Although USB 2.0 can theoretically operate at 480 Mbits/s, tests indicate that this speed is rarely attained. This is possibly caused by the client-server architecture of USB, as opposed to the peer-to-peer network operation of FireWire, and the support for memory-mapped devices in the latter, which allows high-level protocols to run without forcing numerous interrupts and buffer copy operations on host CPUs. Cable length is limited to 4.5 metres (about 15 feet), although up to 16 cables can be daisy chained using active repeaters, external hubs, or internal hubs often present in FireWire equipment. The S400 standard limits any configuration's maximum cable length to 72 meters.

FireWire 800 (Apple's name for the 9-pin "S800 bilingual" version of the IEEE 1394b standard) was introduced commercially by Apple in 2003. This newer 1394 specification and corresponding products allow a transfer rate of 786.432 Mbit/s with backwards compatibility to the slower rates and 6-pin connectors of FireWire 400.


The full IEEE 1394b specification supports optical connections up to 100 metres in length and data rates all the way to 3.2 Gbit/s. Standard category-5 unshielded twisted pair supports 100 metres at S100, and the new p1394c technology goes all the way to S800. The original 1394 and 1394a standards used data/strobe (D/S) encoding (called legacy mode) on the signal wires, while 1394b adds a data encoding scheme called 8B10B (also referred to as beta mode). With this new technology, FireWire, which was arguably already slightly faster, is now substantially faster than Hi-Speed USB.