In this feature we'll take a look at Firewire and examine how the latest 1394b version performs.
Firewire ports have become a standard fitting on most PCs, and while its higher licensing and hardware costs have seen the more affordable USB interface employed by most peripherals, Firewire has carved a niche for itself in more specialist areas.
Firewire, also known as iLink, or by its official name IEEE-1394, has become the dominant standard for connecting DV camcorders to computers and transferring video between them. It’s also employed by many external hard disks, although normally in addition to a USB port.
In terms of raw data rates, the original Firewire specification of 400Mbits/sec may be slightly beaten by USB2’s 480Mbits/sec, but it features several key benefits: Firewire can operate without a host, allowing devices such as DV camcorders to be connected directly to each other for data transfer without a PC or Mac in sight.
The full-size, six-pin plugs can also deliver up to 45 watts of power to devices, allowing much hungrier peripherals to be powered by the port alone, although the mini four-pin ports employed by most camcorders omit the pins that supply the power.
Perhaps the greatest benefit Firewire has over USB is the ability to operate in an isochronous manner. This allows the interface to guarantee bandwidth to the connection, preventing dropped frames when working with real-time applications.
While Firewire has become an invaluable resource for anyone editing video or connecting external hard disks, most ports employ the original 400Mbits/sec specification. As long ago as May 2001, though, the 1394 Trade Association announced its successor, 1394b, and renamed the original spec to 1394a to differentiate them.
Bandwidth boost
1394b doubles the bandwidth to 800Mbits/sec initially, with the potential for
speeds up to 3.2Gbit/sec in the future. It also greatly improves on 1394a’s
maximum cable length of 4.5m by optionally exploiting Cat-5 or fibre cabling to
support lengths up to 100m.
The first peripherals to employ 1394b, or Firewire 800, arrived in 2003, but the interface is still relatively uncommon on PCs, with most motherboards still only offering 1394a. So while owners of the latest Mac or high-end PC may have Firewire 800 connectivity as standard, most of us will need to fit an optional expansion card.
Several manufacturers produce Firewire 800 expansion cards, with some offering a combination of Firewire 800 alongside original Firewire or even USB2 ports. These cards are also normally available in PCI, PCI Express or Express Card versions (the latter for laptops), with most costing between £40 and £55 each at the time of writing.
Some PCI cards may not support the full speed of Firewire 800, though, especially when fitted in a 32-bit slot, so always check the manufacturer’s specifications as some may demand a 64-bit PCI slot. To play it safe, we advise sticking to PCI Express.
Firewire 800 cards will also normally be fitted with an internal power connector in order to deliver power to external devices through the actual Firewire port. Connecting this plug to your PC’s power supply is optional, but if you want to support devices that are port-powered, then you’ll need to wire it up.
In terms of drivers, you may already have everything you need. The most common Firewire 800 Texas Instruments chipsets can use the existing OHCI Compliant IEEE 1394 Host Controller driver built into Windows XP and Vista, so in most cases there’ll be no need to install additional drivers.
