For Fast, Easy Computing, USB Is the Bus to Ride

Connect devices with a USB hub; a utility for cache management; an old AGP card in a new AGP slot.

Lots of things get better with time: friendship, a fine cabernet, and yes, even PCs. Every day we're bombarded by advertisements hawking systems that are faster and cheaper--so much so that it's easy to lose sight of really useful improvements, like the Universal Serial Bus.

USB is the way to connect anything to your PC. It's fast, simple, and so much better than parallel and serial ports that they look downright medieval by comparison. (Not to say that leeches and a good suit of armor don't come in handy every now and then. But, hey, enough about my personal life.) Judging from all the e-mail I get about problems with parallel and serial ports, a surprising number of you still aren't aware of just how great USB is. And with USB 2.0, the spec gains even more advantages. Here's a rundown on why you should be riding with USB.

Ease of use: USB just works better. Period. Getting hardware to function on a serial or parallel port often requires a complicated configuration. USB avoids the hassles of setting and juggling IRQs and other resources. One IRQ covers all the hardware attached to each USB port. USB peripherals have fewer compatibility problems than peripherals using serial or parallel ports.

Speed: A USB 1.1 controller transfers data at up to 12 mbps, or about four times faster than the speediest parallel port and 100 times quicker than a serial port. While that won't affect the performance of a mouse or joystick, it makes a big difference with printers, scanners, and other data-hungry peripherals.

Portability: All USB devices can be hot-swapped, which means that you can plug a piece of hardware into your PC, or unplug one, while your system is running. The operating system will automatically recognize and configure new USB devices.

Support for old hardware: There once was a lack of USB peripherals, but now almost every I/O device comes in a USB version. Even old devices run off USB by using an adapter that converts parallel, serial, and other devices to USB. Belkin and SIIG are two vendors that offer such adapters.

One port, many devices: With the use of a USB controller, a single USB port can theoretically support up to 127 different devices, although practically speaking, it's unlikely you'll ever run more than ten peripherals at one time. All the devices connected to a USB 1.1 controller have to share its 12-mbps bandwidth. If you need to run multiple devices that eat up more than 12 mbps, you can use a PCI adapter card to add a USB controller to your PC. Belkin sells a USB 1.1 PCI adapter card for $39 and a USB 2.0 version for $59.

Easy linking: If you've ever tried to chain together two devices--such as a printer and a Zip drive--you know it can be a real nightmare. USB allows any device to be connected to any other USB device that has a built-in hub. So you'll never have to crawl under your desk to reach the back of your PC when attaching a peripheral.

Some keyboards and monitors have built-in hubs with one or two USB ports. If you don't already have one of these, consider buying a dedicated USB hub that sits on your desktop. Dedicated hubs have clusters of two, four, or more ports. Belkin's four-port USB 2.0 hub, for example, costs as little as $52 online (see FIGURE 1). If your hub connects lots of USB devices to your PC, make sure you have adequate power to run them all. Printers and many similar devices have their own power connections, but mice, keyboards, modems, and others get their power from the USB connection. If the devices need more power than the USB port can deliver, the entire bus may shut down. When this happens, Windows displays a warning icon next to the Universal Serial Bus Controller entry in Device Manager. Fortunately, you can avoid power problems by using the right type of USB hub.

Bus-powered USB hubs draw electricity from the incoming USB connector and output up to 100 mA per port (that's milliamps, a measure of electrical current). Self-powered hubs draw their own power or, in the case of the root hub in your PC, get it from the PC. They provide up to 500 mA per port. Keyboards, mice, and other low-power USB devices use 25 mA to 40 mA and run well on a 100-mA port of a bus-powered hub. More-demanding devices need to use a self-powered hub.

If you buy a self-powered hub, make sure it provides a full 500 mA to each port--some don't. To check, divide the hub's total amperage rating (found in its documentation or on the power supply) by the number of ports. For example, a four-port hub should provide at least 500 mA per port, or 2 amps total.

If your PC originally shipped with Windows 98 or later, it almost certainly has a set of working USB ports. Look on the back of your PC for two narrow, rectangular openings. If you have an older system without USB, an adapter card should get you up and running. (Using USB on systems running Windows 95 is, at best, problematic. If that's what you're using, consider an OS upgrade.)

Many PC peripherals now support the USB 2.0 specification. USB 2.0 devices can run more than 40 times faster than those using USB 1.1. The top USB 2.0 data rate is 480 mbps, which is faster than the IEEE 1394 (FireWire) ports that run hard drives, digital still and video cameras, and CD-RW drives (see FIGURE 2).

USB 2.0 products are backward compatible, so you can use older USB devices on a USB 2.0-equipped PC. So what's the catch? USB 2.0 products are a bit more expensive. Also, the selection of USB 2.0 devices is limited at present, and they require a USB 2.0-ready PC to run them.

Look for the first USB 2.0-ready motherboards and systems to hit the market sometime this spring. You can add USB 2.0 functionality to your system now by using one of the adapters mentioned above. But before buying a USB 2.0 product, check with the vendor to confirm the availability of USB drivers for your operating system. As I write this, USB drivers for Windows XP are still unavailable, and drivers for Windows 98 and Me aren't always included with USB products.

Kirk Steers is a PC World contributing editor. Reach him at kirk_steers@pcworld.com. Hardware Tips welcomes your tips and questions and pays $50 for published items.

Any AGP Port in a Storm?

My brother just gave me his old Pentium III PC minus a graphics card. I opened up its case to add the AGP 2X graphics card I took from my former computer, but the AGP slot in the P-III PC is much longer than the slot in my old system. Can I safely add my old graphics card to the newer computer's AGP slot?

Peter Miller, Topeka, Kansas

You probably can, but before adding an old AGP card to a new motherboard, make sure the two are compatible.

There are three different types of AGP slots: the original AGP 1.0 1X/2X slot, the AGP 2.0 2X/4X slot, and the AGP Pro slot. The 1X/2X version is the shortest and can be distinguished from the 4X type by a small separator that divides it into two sections. The 4X slot also has extra pins at one end.

From your description, your PC probably has an AGP Pro slot. These slots have an extension added to the end of the 4X slot without the extra pins. While the AGP Pro slots are designed for top-end graphics cards costing over $1000, they are also found frequently on motherboards used in mainstream PCs.

Because the AGP Pro slot is backward compatible, a 1X/2X or 2X/4X AGP card will work in the slot. But take care when inserting a 1X/2X card to avoid incorrectly inserting it into the AGP Pro extension. Often these extensions come with a cover to prevent this, but the covers can fall off.

Also make sure your graphics card and motherboard support the same operating voltages. The original AGP 1.0 spec called for motherboards and cards that operate at 3.3V, and the AGP 2.0 spec added support for operation at 1.5V. If your old graphics card operates at 3.3V, you'll need a motherboard that supports 3.3V AGP. Likewise, a card that runs at 1.5V needs a corresponding AGP slot.

Fortunately, many motherboards come with 'universal' AGP slots that support either voltage, and many of the latest graphics cards support both voltages as well. Not all setups do, however. A few motherboards out there run exclusively at 1.5V and won't support the older 3.3V cards. Check with your motherboard and graphics card vendors to determine your hardware's precise requirements.

Spend Your Cache Wisely

When your PC uses the same chunk of data over and over, it often stores that piece of information in fast memory, or cache, where it can retrieve the data faster than it can off a hard drive. Storing the right amount of data in the cache can improve your PC's performance. Outer Technologies' $10 Cacheman is an excellent shareware utility that lets you conveniently monitor memory use and control your cache settings.