Why FireWire is Hot! Hot! Hot!

Francis Vale

Every now and then, a new enabling technology comes along that perfectly epitomizes a new trend. It ultimately could turn out not to be completely successful in the marketplace -- technical worthiness notwithstanding -- but its impact will long be felt.

Such is the case with IEEE P1394, or FireWire. This new technology enables isochronous service while providing the bandwidth needed for audio, imaging, video, and other streaming data. Isochronous service means it guarantees latency; the length of time between a requested action and when the resulting action occurs -- a critical feature in supporting real time video, for example. FireWire provides a high-speed serial bus with data transfer rates of 100, 200, or 400Mbps.

FireWire offers a standard, simple connection to all types of consumer electronics, including digital audio devices, digital VCRs and digital video cameras; as well as to traditional computer peripherals such as optical drives and hard disk drives.

FireWire supports up to 63 devices on a single bus, and connecting to a device is as easy as plugging in a telephone jack. In addition, FireWire provides users with the ability to instantly connect devices without first turning off their machines. Another key feature of FireWire is its ability to stream A/V data off a hard disc in real time, without computer assistance. The protocols also include device-specific commands to start and stop camcorders and VCRs, and other tasks

It is worthwhile to compare FireWire to SCSI, a popular serial bus. The SCSI bus requires that devices be serially daisy-chained together, with each device having a non-conflicting, pre-assigned address, and that the final SCSI device be terminated. But FireWire devices can be connected in multiple configurations. These can include a star or tree pattern with its own daisy chain branches. Device terminators are not required. And FireWire addressing, unlike SCSI, is done dynamically; there is no need for address pre-assignment. All together, FireWire allows up to 1,023 buses to be bridged together.

Originally developed by Apple Computer, more than 60 vendors now belong to the 1394 Trade Association. Computer companies backing FireWire include Apple, Adaptec, Advanced Micro Devices, AT&T, Cirrus Logic, NCR, IBM, Lexmark, Microsoft, Molex, National Semiconductor, Philips, Seagate, Skipstone, and Texas Instruments.

Skipstone (Austin, TX) is shipping a FireWire development toolkit, the TK-10. In addition to a Windows-based SDK, the TK-10 also contains Skipstone's PCI-10 adapter, a high performance intelligent controller for interfacing an IEEE 1394 serial bus to PC's supporting the PCI (Peripheral Component Interface) bus. The PCI local bus is the new computer industry standard for high speed data transfers.

FireWire continues to gain significant industry support, as indicated by the large number of companies who announced FireWire-enabled systems at last Fall's Comdex.

The main mind share competitor to FireWire is Intel's new Universal Serial Bus. But the much touted USB can only achieve data transfer rates of 12 megabits/second, at best; vs. 100 mbs to 400 mbs for FireWire. As opposed to handling multimedia, the USB is better used for doing chores such as computer telephony, handling keyboard and mouse I/O, etc.

Hopefully, FireWire's acceptance also means the end of some truly brain dead consumer electronics interfaces, like the ubiquitous Toslink found on many laser discs and CD players; as well as a hopeful farewell to SP/DIF (Sony/Philips Data Interface).

Mr. Gary Hoffman, President of Skipstone, and the chairman of the 1394 Trade Association, has predicted that FireWire will become a standard consumer electronics interface in 1996. A number of Japanese consumer electronics companies are backing FireWire, including Sony, Matsushita, Mitsubishi, FujiFilm Microdevices, Panasonic Communications & Systems Co., Canon, Toshiba, and Yamaha. (Yamaha is working on a music local area network, called mLAN, which will support a 32 channel digital audio/MIDI architecture over FireWire).

Sony has now shipped a FireWire-equipped, Digital Video Cassette format (DVC) camcorder. This $4,199 (retail) unit is called the DCR-VX1000. With DVC's 500 lines of resolution and a signal to noise ratio of 54dB, the quality of this digital video/audio unit is twice as good as Betacam SP component systems costing almost three times as much.

With FireWire, the link from the DVC camcorder into the computer is direct. This camcorder therefore saves you the expense of buying a high quality video capture PC board with component I/O. And because you can edit right on your computer (provided you have a DVC format encoder/decoder board, and QuickTime or AVI software) it also eliminates the need for a Betacam editing deck. Add it all up, and the DCR-VX1000 saves you more than $20K.

Sony also has a new, FireWire-fitted, color video camera coming out for teleconferencing applications. Sony calls its FireWire hookup a Digital Video (DV) interface.

Other consumer electronics manufacturers are also readying digital camcorders, digital VCRs, and CD ROMs that sport the DV FireWire. Early models of digital VCRs with DV FireWire interfaces already exist in Japan. But like consumer DAT drives, which had to be functionally neutered by SCMS (which only allows first generation copies -- it prevents making copies of copies) the FireWire/Digital VCRs are too good at their job.

The industry pundits say the professional quality tape recordings of these new products will likely raise the ire of the Entertainment industry. As a consequence, analysts think the entrance into the U.S. market of FireWire-equipped, digital VCR's will be delayed; just like DAT drives were for several years.

Apart from FireWire Paranoia Politics, there are some technical issues that may have to be faced. The isochronous-data service of P1394 provides an 8-kHz reference and guarantees bandwidth. This has a possible downside.

National Semiconductor published a design brief that said: "There is a design issue of reducing the jitter in this bandwidth. This is relatively easy to accomplish with low-bandwidth bit streams, such as 64 kbits/s to 384 kbits/s; but with larger bandwidth streams that are not synched to the 8-kHz world, such as MPEG-2 digital video streams, large amounts of buffering may be required." Editor's Note: This NSC Brief information is now out of date. See Letter to Editor

NCR also noted that when doing isochronous transfers over the PCI, a heavily loaded PCI bus can cause problems. As a consequence, you may have to buffer heavily on both sides to account for PCI's latency.

So computer designers using FireWire are probably be wise to modify their PCI connections accordingly. Is this a slam on the 32 bit, 33 MHz, 132 megabyte/sec PCI? No, not when you consider the miserable ISA/EISA PC alternatives. If you are a PC vendor, you just consider using multiple PCIs. E.g., use a low-latency PCI just for video and other such low-latency high-bandwidth signals.

But putting aside all the techno-speak, stop to consider the implications of ubiquitous 100 to 400 megabit/sec FireWire hookups:

1) The home consumer A/V center now supports real time, all digital, professional quality recordings, and does so via low cost systems.

2) The real time, multimedia data streams can now be directly coupled into inexpensive digital processing systems.

3) Which systems in turn are hooked into 10+ MB/Sec Internet modems, like those coming shortly from TV cable companies. And,

4) All of this rich, new, bi-directional content is displayed on the-soon to-be-here, digital-ready, 34" to 60", flat panel TV displays.

The result? In 1997, the definition of High Definition TV might instead be 'PC'.

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Copyright 1996, Francis Vale, All Rights Reserved,

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