Tech Files
FireWire: Birth of a Notion
The emergence of PC multimedia in the 1990s created an intense demand for a low-cost, high-speed, bi-directional cabling standard to replace the aged and notoriously slow serial communication. This demand led to the amazing IEEE 1394 standard, better known by the name FireWire.
Apple Computers designed FireWire, and the IEEE standardized it at the end of 1995. Even though FireWire has existed as a standard for many years, only now do we see wide adoption of the standard.
FireWire consists of a special 6-wire cable and a unique, FireWire-only connector as shown in Figure 1. Sony Corporation has also developed a smaller, 4-pin version.
Figure 1: FireWire connectors (Click images for larger versions)
The 6-pin connection provides power in addition to data transfer, while devices that use the 4-pin version must use a separate power supply. You can purchase cables that convert from the Sony 4-pin to the standard 6-pin connection.
Most devices use the larger standard connector, while the smaller one is found on devices such as Digital Video cameras; in fact, this is one of the most popular uses for FireWire. Any single FireWire cable can be no longer than five meters, often quoted as 15 feet in the United States.
IEEE 1394 allows devices to run at speeds of 100, 200, and 400 Mb/sec, although virtually all FireWire devices now use the 400 Mb/sec speed. Since almost no PCs have built-in FireWire ports, you usually need to purchase a FireWire adapter card as shown in Figure 2.
Figure 2: FireWire adapter card
Note that this card has three controllers. FireWire supports daisy chaining, allowing up to 63 devices to run from a single controller. FireWire is totally hot-swappable and fully compliant with Plug and Play, making it amazingly simple to use.
- Mike Meyers