What Is a FireWire® Bus?

A FireWire® bus is a type of interface that enables various electronic devices to connect to each other by means of high-speed digital data cables, without the need for a computer to mediate. FireWire® can transmit data at speeds up to 800 Megabits per second (Mbps), which translates to a theoretical maximum data transmission rate of 100 megabytes per second. It first appeared in the marketplace in 1995, and it is primarily used for audio and video devices such as digital video cameras. FireWire® is compatible with all of the major computer operating systems and some lesser-known operating systems.

Apple, Inc., formally known as Apple Computer, designed the FireWire® bus in 1986 as a means to increase hard drive data transfer speeds. The Institute of Electrical and Electronics Engineers (IEEE) organization subsequently joined in its development and production, giving it the generic name IEEE 1394. The IEEE founded the IEEE 1394 Working Group, which subsequently managed the development of the technology, with help from Digital Equipment Corporation (DEC), International Business Machines (IBM), Sony Corporation and Texas Instruments.

FireWire® technology allows devices to communicate with each other as peers. This enables interaction between devices when both of them have FireWire® connectivity, such as a digital camera sending photos directly to a printer without an intermediary computer. FireWire® devices can also connect via a daisy chain, which means that they can connect in a peer-to-peer setup, such as a computer connecting to a camera that is directly connected to a printer. In addition, FireWire®-enabled devices can connect in a tree hierarchy, which means that a computer can connect with a camera and a printer and then connect to another computer with a printer and a scanner.

The FireWire® bus comes in two major implementations, which are FireWire® 400, also known as 1394a; and FireWire® 800, known as 1394b. FireWire® 400 transfers data at a maximum speed of 400 Mbps, FireWire® 800 has a top bandwidth of 800 Mbps, and both use 64-bit addressing. As a result of their peer-to-peer connectivity, both buses allow for features such as networking between two computers without the need for an intermediary router or network hub. A FireWire® port provides as much as 45 watts of energy to connected devices, which can free them from the need for their own power supply.

Devices that use FireWire® bus technology enjoy a variety of advantages over previous analog and digital data connection technologies. These improvements include the use of smaller, lighter cables, ease of use and superior speed. In addition, all data is transferred digitally, offering a superior quality of data transmission over standard audio and video cables. It has advantages over other bus technologies, including the ability to hot swap devices, which means there is no need to turn off a computer or a printer to disconnect a FireWire®-based hard drive. Real-time data transmission is another advantage when it comes to applications such as capturing and recording live video footage.

There are certain limitations that exist with regard to the design of FireWire® technology. For instance, only 63 devices can connect via a singe FireWire® host device. The maximum length for a FireWire® 400 cable is a little less than 15 feet (about 4.5 m), and the maximum length for a FireWire® 800 cable is 330 feet (100 m). Although the FireWire® bus can provide as much as 45 watts of power, this is not enough to supply the 63 devices that can connect to the bus, which means that some devices will need to have their own power sources.