Storage Toolkit

More wires, more fire: FireWire 800

Jon L Jacobi CNET

Published: 05 May 2005

You may not have noticed, but there's a new kind of FireWire in town: FireWire 800. Based on the IEEE 1394b standard, it doubles the old maximum FireWire transfer rate from 400 megabits per second (Mbps) to 800Mbps. Although IEEE 1394b was introduced in 2000 and the first products shipped in 2002, the specification only recently started to gain momentum in the PC mainstream. Even now, FireWire 800 controllers ship only on high-end Macs, one or two PC motherboards, and a few adapters from vendors such as Adaptec and Belkin.

The technology is getting the most play with external hard drives, such as the Iomega External Hard Drive and the LaCie d2 Hard Drive Extreme, which harbour bridge chips that allow the ATA hard drives inside these boxes to communicate over the FireWire bus.

What's in a name?
Before we go any further, let's clear up the FireWire/IEEE 1394 naming issue. FireWire is like Kleenex in that it's a brand name. Apple coined it for the company's products based on the IEEE 1394 standard, just as Sony did with its iLINK interface. Apple no longer charges for the name, so, since FireWire is sexier and a lot easier to say than IEEE 1394, it's now the marketing moniker of choice for the technology. The upshot is that FireWire, iLINK, and IEEE 1394 (a.k.a. High Performance Serial Bus/HPSB) are completely compatible with each other and may be mixed together freely. Also, the so-called DV port on digital video cameras is actually a FireWire port used for transmitting DV-format video data.

Upping the ante
FireWire 800's 800Mbps transfer rate is the third speed bump in the FireWire saga. The initial IEEE 1394-1995 (for the year) and follow-up IEEE 1394a standards allowed for 100Mbps, 200Mbps or 400Mbps (the actual speed is about 2 percent slower, but it's rounded up to make things easy). The first drives and chips to hit the market used the two slower speeds. It took a year or two for faster 400Mbps chips and peripherals to show up, and these FireWire 400 components are currently the de facto standard. The bump to 800Mbps is only the tip of the IEEE 1394b iceberg -- the standard also provides for faster 1.6Gbps and 3.2Gbps transfer rates across copper wire. And transmission rate is only part of the picture; also in the works are a new encoding/compression scheme and simultaneous transmit and receive, plus a few other new tricks.

Along with newfound speed, IEEE 1394b extends the old 4.5-metre transmission limit to 100m with new cabling. Legacy IEEE 1394 cables normally come in a 6-pin configuration with two twisted signal pairs and a negative/positive power pair, capable of providing 50 watts of DC for powering peripherals (USB 2.0 provides only 1.5 watts). The smaller 4-pin connectors you find in cameras and other self-powered peripherals omit the power. The new 9-pin IEEE 1394b cables use 2 pins to attach a grounded shield that surrounds the other wires and prevents interference from outside electromagnetic noise, which helps speed up data transmission rates by reducing crosstalk. The third new pin is unused (the 1394b committee decided to use a pre-existing cable technology and didn't want to force cable makers to tool up for eight conductor cables and connectors). IEEE 1394b is backwards compatible, so you'll also find 9-pin-to-6-pin and 9-pin-to-4-pin adapter cables. Alas, you won't get the higher speed of FireWire 800 if you attach legacy peripherals to what's called a 'bilingual' port (it speaks both IEEE 1394a and b). The newer b-only, or beta, ports don't support older IEEE 1394 devices. Due to slight physical differences between b-only and bilingual connectors, a bilingual port can take both FireWire 800 and older FireWire connectors, while a b-only port will take only a FireWire 800 connector.

What does this mean for you?
Theory is fine, more efficiency is great, but what real-world benefits does FireWire 800 offer? According to our anecdotal tests, for the average user, there are almost none. With external single hard drives that support both FireWire 400 and 800, our test results have been mixed, with FireWire 800 slightly faster in some cases and slightly slower in others. However, if you're accessing more than one external drive, as in a RAID box or a multi-drive setup, the doubled bandwidth should provide a noticeable improvement in performance. How much we can't say yet, but we'll report back when we've completed testing. For now, FireWire 800 is a power-user technology.

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