Connection systems: The numbers game

If you're fed up of waiting an eternity every time you want to download from your digital video camera, you'll need a good connection system. But which one really is the fastest? Charles Arthur reports

If you're shopping for a new computer, or peripherals such as a scanner or camcorder in the next few months, you'll probably encounter salespeople talking about a connection system called USB 2.0, and comparing it with one called "FireWire" (or vice-versa). Your problem: disentangling what's true from what's not – and especially, getting some value for money. USB 2.0 is being dressed up as a new superfast communications system that will let your peripherals transfer data faster even than the evocatively named FireWire. For where FireWire's present maximum speed is 400 megabits per second, USB 2.0 claims 480Mbps.

If you're shopping for a new computer, or peripherals such as a scanner or camcorder in the next few months, you'll probably encounter salespeople talking about a connection system called USB 2.0, and comparing it with one called "FireWire" (or vice-versa). Your problem: disentangling what's true from what's not – and especially, getting some value for money. USB 2.0 is being dressed up as a new superfast communications system that will let your peripherals transfer data faster even than the evocatively named FireWire. For where FireWire's present maximum speed is 400 megabits per second, USB 2.0 claims 480Mbps.

Wow! Bigger number alert! So USB 2.0 is the winner, right? Actually, no. As so often with computing, numbers do not tell the full story. Just as with megahertz and processor speeds, "faster" doesn't necessarily mean you'll get more done.

You're far more likely to have come across USB than FireWire. USB, of course, is the simple plug-and-play method for connecting your computer to things such as mice, PDAs, cameras and, if you want, hard disks. Up to 127 devices can be linked to a single computer (if you're mad, or rich) and you can power small things like Webcams using its output of about five watts.

Proponents of USB 2.0 say that USB 1.1, which is what you'll find in computers today, is slow – only 12Mbps transfer speed. That's good enough to play an MP3, or download small digital pictures, but if you're doing a lot of those, or moving really big files (movies, big collections of pictures) around, that 12Mbps bottleneck will throttle you.

So, they say, move on up to USB 2.0, which is up to 40 times faster, and potentially even faster than FireWire.

Which is? Ah, a plug-and-play system for connecting up to 63 devices in a chain – things such as digital video cameras, hard disks, MP3 players (Apple's iPod) and anything that needs to move serious chunks of data around. Sony calls this technology, which it co-developed with Apple Computer, "i.Link"; the official name is IEEE1394a. Its power output of up to 60 watts can drive hard disks and recharge batteries.

The crucial difference between USB 2.0 and FireWire is this: FireWire is faster and more reliable. The reason is subtle, and not mentioned at all by the proponents of USB 2.0. Moving data around using USB demands the involvement of a processor. FireWire doesn't. If you're trying to download a digital video from your camcorder on to your hard disk to edit it, then with USB 2.0 each chunk of data has to pass to your processor and then to the hard disk. With FireWire, the hard disk and the camcorder talk directly to each other.

By contrast, if you even move your mouse (especially a USB mouse) while transferring data via USB 2.0, you'll get a hiccup, and "top speed" goes out of the window. Surf the Net while you're doing it, or do any multitasking, and that data is caught in a traffic jam. All of which makes the claims made for USB 2.0 (at sites like www.usb.org and PC Magazine www.pcmag.com) look rather bogus. PC Magazine gives USB 2.0 a prize, saying it "may signal the final push toward a PC market free of PS/2, serial, and parallel ports, eliminating the frequent conflicts that come with them". I'm all for slimming down the number of ports on the back of PCs, but you don't need USB 2.0 to do that; the present version does just fine, allied to FireWire. Prizewinning it ain't.

So why are companies like Dell going to go with USB 2.0 rather than FireWire when it's inferior? Three reasons: first, Apple and Sony still demand a royalty on each FireWire setup, while USB is a "royalty-free" protocol. Second, PC manufacturers hate Apple (even though USB only got popular because it appeared on the iMac in 1998). And Intel, pushing USB, is happy to sell you things that will make your processor look galumphing.

USB 2.0 will probably come built in to future machines. But don't settle for it. Get a FireWire add-on card; the benefits are huge, the cost only £80 or so. Rumours also say that Steve Jobs of Apple will demonstrate the long-delayed FireWire 2 (aka IEEE1394b) with speeds up to 800Mbps later this week. That's really going to be hard for USB to match. Though I'm sure that won't stop USB 2.0 being in big brochures with "NEW!" by its name. Just be careful what numbers you believe.

www.usb.org; www.computer.org/multimedia/articles/firewire.htm