FireWire is Apple Inc.'s brand name for the IEEE 1394 interface (although the 1394 standard also defines a backplane interface). It is also known as i.LINK (Sony's name) and DV (Panasonic's name, not to be confused with DV camcorder tapes). It is a serial bus interface standard, for high-speed communications and isochronous real-time data transfer, frequently used in a personal computer (and digital audio/digital video).
FireWire has replaced Parallel SCSI in many applications, due to lower implementation costs and a simplified, more adaptable cabling system. IEEE 1394 has been adopted as the H
igh Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control[1]. FireWire is also available in wireless, fiber optic, and coaxial versions using the isochronous protocols. Wireless FireWire is being integrated into the WiMedia Alliance's WiMedia Ultra-Wideband (UWB) standard.
igh Definition Audio-Video Network Alliance (HANA) standard connection interface for A/V (audio/visual) component communication and control[1]. FireWire is also available in wireless, fiber optic, and coaxial versions using the isochronous protocols. Wireless FireWire is being integrated into the WiMedia Alliance's WiMedia Ultra-Wideband (UWB) standard.Almost all modern digital camcorders have included this connection since 1995. Since 2003 many computers intended for home or professional audio/video use have built-in FireWire/i.LINK ports, including all Sony computers, all but one of Apple's computers, and most Dell and HP models currently produced. It is also available on many retail motherboards for do-it-yourself PCs.
Technical specifications
FireWire can connect up to 63 peripherals in a tree topology (as opposed to Parallel SCSI's Electrical bus topology). It allows peer-to -peer device communication — such as communication between a scanner and a printer — to take place without using system memory or the CPU. FireWire also supports multiple hosts per bus. It is designed to support Plug-and-play and hot swapping. Its six-wire cable is more flexible than most Parallel SCSI cables and can supply up to 45 watts of power per port at up to 30 volts, allowing moderate-consumption devices to operate without a separate power supply. (As noted earlier, the Sony-branded i.LINK usually omits t he power wiring of the cables and uses a 4-pin connector. Devices have to get their power by other means.)
FireWire devices implement the ISO/IEC 13213 "configuration ROM" model for device configuration and identification, to provide plug-and-play capability. All FireWire devices are identified by an IEEE EUI-64 unique identifier (an extension of the 48-bit
Operating system support
Full support for IEEE 1394a and 1394b is available for FreeBSD, Linux, Apple Mac OS 8.6 through to Mac OS 9[5], and Mac OS X as well as NetBSD and Haiku. Microsoft Windows XP supports both, but as of Service Pack 2, each FireWire device will run at S100 (100 Mbit/second) speed. A download is available from Microsoft which enables devices rated at S400 or S800 speeds to operate at their rated speed.[6] Some FireWire hardware manufacturers also provide custom device drivers which replace the Microsoft OHCI host adapter driver stack, enabling S800-capable devices to run at full 800 Mbit/s transfer rates. Microsoft Win
dows Vista currently supports only 1394a, with 1394b support coming later in a service pack. (Vista SP1 RC1 is available from mid December 2007, with full release expected during the first quarter of 2008)
dows Vista currently supports only 1394a, with 1394b support coming later in a service pack. (Vista SP1 RC1 is available from mid December 2007, with full release expected during the first quarter of 2008)Comparison to USB
Although high-speed USB 2.0 runs at a higher signaling rate (480 Mbit/s) than FireWire 400, typical USB PC-hosts rarely exceed sustained transfers of 35 MB/s (280 Mb/s), with 30 MB/s (240 Mb/s) being more typical (the theoretical limit for a USB 2 high-speed bulk transfer is 53.125 MB/s). This is likely due to USB's reliance on the host-processor to manage low-level USB protocol, whereas FireWire automates the same tasks in the interface hardware. For example, the FireWire host interface supports memory-mapped devices, which allows high-level protocols to run without loading the host CPU with interrupts and buffer-copy operations.[13]
FireWire 800 is substantially faster than Hi-Speed USB.
