What is FireWire or IEEE 1394?
FireWire is a high-speed serial bus, developed by Apple and Texas Instruments, that allows for the connection of up to 63 external devices. FireWire is also commonly known as the IEEE 1394 standard. FireWire, which Apple originally developed and trademarked, may appear under different names (such as iLink or Lynx) depending on what platform or company implements the technology. The original IEEE 1394 specifications allowed for speeds of 100, 200, and 400Mbps (million bits per second). IEEE 1394b provides speeds of 800, 1600, and 3200Mbps.
This makes IEEE 1394 a very high-speed bus design that is ideal for high-bandwidth applications like multimedia. In addition to providing high-speed access, IEEE 1394 supports Plug and Play connections, hot swapping, multiple speeds on the same bus, and isochronous data transfer, as well as providing power to peripheral devices. Hot swapping is the ability to add and remove devices to a computer while the computer is running and have the operating system automatically recognize the change. Isochronous data transfer is a means of transferring data at a guaranteed transfer rate. This is especially useful for devices that require transferring large amounts of data in real time, such as video cameras or digital cameras.
Advantages of IEEE 1394
- Real-time data transfer for multimedia applications
- 100, 200, and 400Mbps data rates currently; 800Mbps and multi-Gbps
upgrade path
- Live connection/disconnection without data loss or
interruption
- Automatic configuration supporting Plug and Play
- Guaranteed bandwidth assignments for real-time
applications
- Common connectors for different devices and applications
- Uses a six-wire, shielded twisted-pair cable that can be up to 4.5 meters in length; IEEE 1394b supports distances up to 100 meters
Note: IEEE 1394b is backwards compatible; if it is used on a network with 1394a components, it will communicate at the slower speeds.
This information was adapted from Texas Instruments' IEEE 1394 High Performance Serial Bus site.
While IEEE 1394 is very fast, it is also expensive to add to computer systems. Typically it costs between ten and twenty dollars to add FireWire controllers and physical links to a system or peripheral. For comparison, adding a USB microcontroller costs less than one dollar. You can think of IEEE 1394 as a high-speed, very flexible, peer-to-peer, enhanced version of USB. While the Windows Driver Model (WDM), which Windows 98 uses, supports drivers for IEEE 1394, it was not fully supported until Windows 2000. Currently, few Wintel systems have IEEE 1394 ports. All Apple Macintosh computers, starting with the blue and white G3s, support FireWire. Interestingly, both Microsoft and Intel are investigating using IEEE 1394 as a replacement for the IDE drive interface.
For additional information on the IEEE 1394 standard, please see:
- Apple's Developer Connection FireWire article
- Embedded Systems Programming's Fundamentals of Firewire
Last modified on May 13, 2009.
