Firewire is Apple's name for the IEEE 1394 Interface, an interface similar to the USB cable interface. Like USB cables, firewire cables allow users to connect peripheral devices like external hard drives, memory card readers, and digital camcorders to their computers. Firewire comes in two speeds, Firewire 400 and Firewire 800, both of which are significantly faster than USB. Although most Windows-based PCs don't ship with firewire ports as standard, Apple computers tend to have firewire ports, and some newer Apple computers ship with both Firewire 400 and Firewire 800 ports.
There are two kinds of Firewire 400 connectors, 6-pin and 4-pin connectors. In general, 6-pin connectors are featured in Firewire 400 ports in computers themselves, while 4-pin connectors are featured in Firewire 400 devices. Accordingly, most Firewire 400 cables feature a 6-pin connector on one end and a 4-pin connector on the other.
In contrast, Firewire 800 ports and cables feature 9-pin connectors. These 9-pin connectors, pictured below right, sit on both ends of the cable, and the connections on computers and devices are almost identical.
Firewire 400 and Firewire 800 Differences
Firewire 800 ports and cables can communicate up to about twice the speed of Firewire 400 ports and cables. Firewire 800 ports are backwards compatible with Firewire 400 devices, meaning that Firewire 400 devices can be used with Firewire 800 ports. However, Firewire 800 ports feature a different, 9-pin connector, meaning that a special "bilingual cable" must be used to connect Firewire 400 devices to Firewire 800 ports. It's easy to differentiate between Firewire 400 and 800 ports and cables. Firewire 400 ports and cables feature 6-pin and 4-pin connectors, pictured top right, while Firewire 800 cables and ports feature 9-pin connectors, pictured right.