Hardware Reference
In-Depth Information
hubs that also contain various combinations of other port types. These special hubs are
more expensive than USB-only hubs but are less expensive than the combined cost of a
comparable USB hub and two or more USB adapters.
Another type of adapter available is a direct-connect bridge cable, which enables you to
connect two USB-equipped PCs directly using USB as a network. These are popular for
transferring files because this connection usually works as well or better than the direct
parallelconnectionthatotherwisemightbeused.AlsoavailableareUSBswitchboxesthat
enable one peripheral to be shared among two or more USB buses. Note that both the
direct-connectcablesandUSBswitchboxesaretechnicallynotallowedaspartoftheUSB
specification, although they do exist.
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 offi-
cially called 1394, it was initiated under the trademarked name FireWire by Apple Com-
puter, who made most of the initial contributions to the design. The 1394 is the result of
the large data-moving demands of today's audio and video multimedia devices. 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 Standards
The most popular version of the 1394 standard is actually referred to as 1394a, or some-
times as 1394a-2000 (for the year this version was adopted). The 1394a standard was in-
troduced to solve inter-operability and compatibility issues in the original 1394 standard;
it uses the same connectors and supports the same speeds as the original 1394 standard.
Thefaster1394bstandardwasintroducedinearly2003,andisfullybackwardcompatible
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 tech-
nology. Originally, the term
FireWire
was an Apple-specific trademark that Apple li-
censedtovendorsonafeebasis.However,inMay2002,Appleandthe1394TradeAsso-
ciation 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
