Hardware Reference
In-Depth Information
keyboards, and pointing devices such as mice and trackballs.
IEEE 1394 (FireWire or i.LINK)
The Institute of Electrical and Electronic Engineers Standards Board introduced IEEE 1394 (or just
1394 for short) in late 1995. The number comes from the fact that this happened to be the 1,394th
standard the board published. Although the standard is officially called 1394, it was initiated under
the trademarked name FireWire by Apple Computer, who made most of the initial contributions to the
design. The key advantage of 1394 is that it's extremely fast; the current standard supports data-
transfer rates up to 400Mbps (1394a), 800Mbps (1394b S800), and 3,200Mbps (1394b S3200).
1394/FireWire is included on many high-end motherboards, and the interface is widely used in
devices such as camcorders, digital video editing equipment and some external drives. More recently
1394 began being supplanted by Thunderbolt Technology in the video editing and production market.
1394 Standards
The most popular version of the 1394 standard is actually referred to as 1394a, or sometimes as
1394a-2000 (for the year this version was adopted). The 1394a standard was introduced to solve
interoperability and compatibility issues in the original 1394 standard; it uses the same connectors
and supports the same speeds as the original 1394 standard.
The faster 1394b standard was introduced in early 2003 and is fully backward compatible with
1394a devices. The 1394 standard is also known by two other common names: FireWire
(trademarked by Apple) and i.LINK (trademarked by Sony).
i.LINK
is an IEEE 1394 designation
initiated by Sony to put a more user-friendly name on IEEE 1394 technology. Originally, the term
FireWire
was an Apple-specific trademark that Apple licensed to vendors on a fee basis. However,
in May 2002, Apple and the 1394 Trade Association announced an agreement to allow the trade
association to provide no-fee licenses for the FireWire trademark on 1394-compliant products that
pass the trade association's tests. Apple continues to use
FireWire
as its marketing term for IEEE
1394 devices. FireWire 400 refers to Apple's IEEE 1394a-compliant products, whereas FireWire
800 refers to Apple's IEEE 1394b-compliant products. Note that Intel has always licensed USB on a
royalty-free basis, which is perhaps the biggest reason it became more popular than FireWire in PCs
and consumer devices.
1394a Technical Details
The IEEE 1394a standard currently exists with three signaling rates: 100Mbps, 200Mbps, and
400Mbps (12.5MBps, 25MBps, and 50MBps). A maximum of 63 devices can connect to a single
IEEE 1394 adapter card by way of daisy-chaining or branching. Unlike USB devices, 1394 devices
can be used in a daisy-chain without using a hub, although hubs are recommended for devices that
will be hot-swapped. Cables for IEEE 1394a devices use Nintendo GameBoy-derived connectors
and consist of six conductors: four wires transmit data and two wires conduct power. Connection
with the motherboard is made either by a dedicated IEEE 1394a interface or by an adapter card.
Figure 14.15
shows 1394a port connectors.
