FireWire - How a Computer Works (2015)

How a Computer Works (2015)

21. FireWire


FireWire Socket

FireWire is the name for an interface which connects devices to your PC. FireWire is particularly useful when transferring large amounts of data to the computer.

Video transfer is a popular use for FireWire.

A card for video use would plug into a vacant PCI slot on the motherboard. FireWire is similar to USB but has some important differences.

Plug and Play


FireWire is plug and play compatible, so when a new device is connected to the computer, Windows auto-detects the device and asks for a driver. If the driver and device have already been installed the computer then starts communicating with the device.

FireWire devices are hot pluggable so they can be connected or disconnected even when the computer is running.



FireWire uses 64-bit fixed addressing. These are the three communication transfers, which make up the data packet when communicating to the computer.

10-bit bus ID. This determines which FireWire bus the data originated from. 6-bit physical ID. Identifies which device on the bus sent the data.

48-bit storage area. This is capable of addressing 256 terabytes of information per node. The bus and physical Ids together make up the 16-bit node ID, this means 64,000 nodes are allowed on a system.



A Hop is when devices are daisy chained together. Data can travel through a maximum of 16 Hops with a distance of 72 metres. For instance a digital camcorder maybe connected straight to an external hard disk, which in turn is connected to a computer.



A FireWire device can draw its power through the FireWire cable. FireWire supports isochronous devices. In isochronous mode, data travels between the device and host in real-time with guaranteed bandwidth. When a device like a digital camcorder is connected into a FireWire system it can request the host provide it with enough bandwidth for the camcorder to send the video without any disruption.

With video transfer to your computer FireWire comes into its own as it enables data to be transferred up to 400Mbps.