Firewire - explained (v1.00)

Firewire
By: Michael Jansen of Kansas State University

Speed is the key to the successful future of any computer device. However, while processor speed has increased 15-fold, PCs still use the same serial port that they did in the 70s. The market has also been calling for one interface to connect all of it's components. The interface that can meet both of these needs is the proposed IEEE standard 1394, called Firewire by its pioneers at Apple. 1394 is compatible with a wide range of devices as well as having speed and price advantages over current data transfer systems.

Even though serial ports have not changed recently, other computer interfaces have changed. One example of improvement in interfacing is that of the Small Computer System Interface (SCSI) bus. Bus refers to the cabling inside the computer. This is a very simplistic view of the term "bus". However, the disadvantages of SCSI based systems are two fold. First SCSI is a parallel interface and second it is an expensive route for computer speed. The SCSI, as well as other parallel buses, have a very limited connectability (only connecting hard drives, CD-ROM drives and tape back-ups).

1394 will at the least replace the "com" port (the current serial port on the back of a PC used to plug in devices such as a mouse or a modem). The applications that 1394 can harness are immeasurable. There may be many applications that are not even thought of in our conventional wisdom because of their lack of feasibility.

The standard is platform independent, partly because the originator of the technology was Apple Computers. Apple trademarked it as Firewire, then IEEE took over by designing the standard. Gary Hoffman, CEO of Skipstone Inc., stated in a speech at COMPCON '95 that besides connecting any platform, the interface can connect almost all computer peripherals such as printers, scanners, modems, keyboards, displays (monitors), hard drives and CD-ROM drive.

Along with these computer peripherals the multimedia market will also support the connection of digital cameras, digital camcorders and televisions, along with all other digital consumer audio and video equipment.

There has always been a compatibility gap between the use of these consumer electronics and computers. Typically a special feature card would be required to translate signals into something that the computer could understand, but now the world can just plug the universal connection (1394) into both the personal computer and consumer electronics.

Video conferencing is one advantage that will be available almost immediately with the implementation of 1394. The digital camcorder already uses 1394 and it would be a simple task to set up a network that could connect several people in a video conference once the PC has been fitted with IEEE 1394.

While video conferencing might only benefit businesses, imagine how this technology could revolutionize the chat rooms on the Internet. Society would now be able to see real-time video of the people they talk to on the Internet. The advantages of real-time transmissions are almost limitless.

Other benefits of the standard include a fast transfer rate and guaranteed bandwidth (bandwidth describes the consecutive frequencies within a band). According to Christopher O'Malley in the July 1994 issue of News & Views, the standard is set up to allow 100 megabits per second (Mbps), 200 Mbps, and 400 Mbps. One gigabit per second is also a possibility for the future. News & Views is a magazine that is published on the World Wide Web.

The 1394 network can support all these rates of transfer simultaneously (this means that 1394 has a scalable architecture). To put these figures into perspective the transfer required for audio and video is in the following table:

Type of Signal         Signal Specific Info     Transfer Required

------------------------------------------------------------------

High Quality Video     30 fps                   221 Mbps

                       640 x 480 pels

                       24-bit color / pel



Reduced Quality Video  15 fps                   18 Mbps

                       320 x 240 pels

                       16-bit color / pel



High Quality Audio     44,100 samples / sec     1.4 Mbps

                       16-bit samples

                       2 channels



Reduced Quality Audio  11,050 samples / sec     0.1 Mbps

                       8-bit samples

                       1 channel



source: Gary Hoffman, CEO of Skipstone Inc.

Chipsets are already able to support 100 and 200 Mbps, with technology for 400 Mbps transfer coming within a year. These transfer rates will allow real-time transmissions. The standard also promises to give guaranteed bandwidth, which will allow real-time data transmissions.

The way the transfer system works involves time segments for transfer, and a priority system that determines what type of transfer and when a transfer of data will begin. If a device requires guaranteed bandwidth (such as a digital video device) isochronous data transfer is used this gives an equal amount of time to the device each cycle (or pass). First, all devices that require isochronous transfer are given a slice of time in the cycle. Then, the remaining time in the cycle is given to asynchronous data transfer, which is divided among the rest of the devices requiring data transfer in the cycle.

The numbers from above show an increase of 2.5 times over current parallel bus systems, such as SCSI and IDE. Also, because the standard is a serial bus it can provide higher resolution and less noise than the parallel systems. The "noise" is due, in part, to the parallel data wires creating electric fields that pass through other wires in the bus.

Another benefit 1394 has over current bus systems is that the 1394 standard is "hot plugable." This means that the network stability is not lost when the user adds or removes devices, thus allowing the user to plug in his digital camcorder without disrupting the data transfer of a 1394 hard drive. This is a function not allowed by SCSI or IDE systems, which would require a system shut down just to plug in the device.

There is also a drastic price advantage in using the 1394 standard over parallel bus systems. One reason for the price difference is that a parallel bus system requires several data wires to be placed side by side, this increases the hardware space, as compared to the number of lines required by a serial bus system. Overall, the components of 1394 will have a definite price advantage over existing high speed bus systems.

The above benefits of the proposed standard have lured several major companies into supporting the standard. This creates another benefit of using 1394: The market is going to support the use of the standard. Without market support good systems will not last, because there would be no point in owning a system that has no peripherals.

Texas Instruments (TI) and Sony are the two front runners in the design of 1394 devices. TI has made a 1394 chipset that can support 100 Mbps and should soon have one for 200 Mbps, with a 400 Mbps and 1 Gbps chipset on the horizon.

Sony has also entered the 1394 market with a digital camcorder that uses the 1394 standard. Some other companies that are backing the IEEE standard are IBM, Maxtor, Microsoft, Skipstone, Toshiba and Yamaha.

The proposed IEEE standard 1394 is a viable solution for the 'speed' needs of our society. Computer designers have been talking about a universal connection for years; 1394 has the potential to fill that Utopian idea. Even if 1394 does not become the only interface that consumers use to connect devices to their personal computer, it does promise to bridge the speed gap that the processors of today have created.

To find more information about the technical aspects of 1394 search the WWW at http://www.ti.com/sc/docs/msp/1394/1394.htm and get a copy of the IEEE standard from IEEE.