The “U” in USB stands for “Universal”, and no other I/O port does so much for so many computer users as USB. From providing a home for keyboards and mice to driving printers, scanners, all-in-one units, and providing access to terabytes of storage and the Internet, USB ports do it all. That also means that USB-related problems can cripple your PC, leaving it unable to access storage, input, and output devices.

Tracking down the causes of USB-related woes can be difficult, but in this article, we show you the common and uncommon causes for USB problems – and their solutions.

USB Troubleshooting 101

Recent operating systems include drivers for common USB devices, such as keyboards, mice, and storage devices. If one of these devices is not recognized when you plug it into a USB port, try another USB port on the computer itself (we’ll discuss troubleshooting ports built into hubs later), preferably a USB port built into the port cluster on the rear of a desktop PC.

If the device works in some USB ports, but not others, note the ports that are not working. This information will be used to help determine if the cause is the hardware setup at the BIOS level or at the Windows driver or Device Manager level.

If the device works on another PC, but not on yours, the problem lies with your PC. However, if the device doesn’t work on any PC, it’s time to replace the cable, or the device itself.

Even if you never have a USB device that doesn’t work at all, you might see one of the following messages when you plug a USB device into your computer or into an external hub:

“This device can perform faster”

To solve this problem, we need to see how USB ports are configured in the system BIOS – and find out what type of USB hub is in use.

“Hub power exceeded”

This problem, on the other hand, requires a trip to the Windows Device Manager.

Diagnosing USB Port Problems in BIOS Setup

BIOS setup is the place to check if you have any of the following USB problems:

- Your system doesn’t recognize a mainstream USB device, such as a printer, mouse, or storage device, in any USB port.

- You get a “This device can perform faster” error message when you plug a Hi-Speed USB (aka USB 2.0) device into any port on a recent computer.

- You can use a USB drive for storage, but you can’t boot from it, and you’ve verified the drive is a bootable device.

- You can use a USB keyboard in Windows, but not for accessing the BIOS at system startup.

To check BIOS settings, restart your computer and press the appropriate key to open the BIOS setup menu.

Tip: If you are unable to access the BIOS setup menu with a USB keyboard, plug in a PS/2 (6-pin DIN) keyboard (if your system has a PS/2 keyboard port). It’s worthwhile keeping an old PS/2 keyboard around for troubleshooting. Some USB keyboards can also be adapted to PS/2.

Checking for “Missing” USB Ports in BIOS Setup

Once you have the BIOS settings menu open, what’s next? Typically, you will find USB port settings in the Integrated Ports or Integrated Peripherals menu:

If the USB controller or host controller is disabled, no USB ports will be recognized by Windows, and consequently no USB devices will be recognized either.

What if some USB ports are usable, but others are not? Some systems enable you to specify the number of USB ports in BIOS setup.

To solve problems with “missing” USB ports, make sure the following settings are enabled:

USB controller

USB 2.0 controller (aka USB EHCI controller)

USB legacy support

Save changes, exit BIOS setup, and your system will restart, providing access to USB ports.

Tip: If you are unable to use a USB keyboard in BIOS setup, but it works after Windows boots, there’s a problem with USB keyboard or legacy support. Change the setting, or contact your system or motherboard vendor for a BIOS update.

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Missing USB 2.0 Support

USB 2.0 support has been included in virtually all systems built in the last five years or so. However, it’s possible to configure a system so USB 2.0 support is disabled.

On most systems that include USB port options in the system BIOS, you can specify whether to run USB ports in 1.1 or 2.0 (Hi-Speed USB) modes. Depending upon the system, you might see separate entries for USB controller and USB 2.0 controller in BIOS setup, or BIOS setup might have a single entry for USB controller with the option to enable 1.1 support only or 1.1/2.0 support.

Make sure USB 2.0 support is enabled, save changes, exit BIOS setup, and your system will restart, providing USB 2.0 support.

Note: If you have an old system that was never updated to Windows XP SP1 or later, its USB 2.0 ports will run only in USB 1.1 mode, regardless of the BIOS setting, until SP1 or later is installed (SP1 added USB 2.0 support). So, if you’re reinstalling Windows XP original edition, make sure you install SP3 immediately, if not sooner (see our article on using the free nLite utility to do this).

Diagnosing USB Power Management Problems

Some systems cannot wake up a system from S3 (deep sleep) power management mode unless this option is enabled in the system BIOS. If you are unable to wake up your system by tapping on a USB keyboard or moving the mouse, make sure this option is enabled in the system BIOS.

Diagnosing USB Problems with Device Manager

If you’re still having problems with some USB ports after making sure that the BIOS settings are correct, the next stop for Windows users is Device Manager.

In Device Manager, USB 2.0 controllers are listed as Enhanced, while USB 1.1 are listed as OpenHCD. Note that a single USB 2.0 controller can manage all USB ports built into the motherboard, while each root hub requires its own OpenHCD controller.

Note: If your system does not have USB 2.0 support enabled in the BIOS, an Enhanced controller entry will not appear in Device Manager.

Root Hubs and Generic Hubs

You won’t find USB ports listed by that name in Device Manager. Instead, Device Manager lists USB ports by host device:

- Root hub

- Generic hub

Root hubs host USB ports connected to the computer’s motherboard or add-on USB host adapter card. A root hub typically hosts two USB ports in 1.1 mode, and the root hub on a system with USB 2.0 support hosts all of the USB ports built into the system. To determine the number of ports a root hub hosts, open a root hub’s properties sheet in Device Manager and click the Power tab.

If a root hub is disabled in Device Manager, devices connected to the hub cannot be used and are no longer displayed in Device Manager.

To enable a disabled root hub, right-click the hub and select Enable from the right-click menu. Follow any prompts displayed to complete the process.

Generic hubs are external devices that host USB ports. A generic hub plugs into a USB port, enabling the port to service multiple devices. By daisy-chaining generic hubs to a root hub, a single USB port can support up to 127 devices.

Generic hubs are available in a variety of forms, from standalone devices that include four or more USB ports to keyboards and monitors that include USB ports. Because some generic hubs are self-powered, and some are bus-powered, generic hubs can cause power problems for some USB devices.

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Hubs and USB Power Problems

One of the most poorly understood causes of USB problems is the difference between self-powered and bus-powered hubs. Self-powered hubs include root hubs (which draw current from the computer’s power supply) and generic hubs that are connected to AC power. These hubs provide 500mA of current to each USB port.

Generic hubs that do not have an AC power source are bus-powered, and provide only 100mA of current to each USB port.

Bus-powered hubs are suitable hosts for USB devices that use little power, such as keyboards, most mice, printers, and external hard disks that use AC power. However, device power requirements vary widely, and other types of popular devices, such as portable hard disks, flash memory drives and card readers, and game controllers with force feedback often cannot operate when plugged into a bus-powered hub.

To determine the power requirements for any USB device, open the Power tab for the root or generic hub the device is plugged into.

The devices shown in this example must be plugged into a self-powered USB hub, as they require more than 100mA of current.

However, the devices shown in this example can be plugged into either a bus-powered or self-powered hub, as they require less than 100mA of current.

Dangers of Exceeding Available Hub Power

If you plug a device that requires more power than the hub can provide, what happens?

If you plug a device that requires more than 100mA of current into a bus-powered hub, you will see a “Hub Power Exceeded” message.

Click the message to see a listing of other ports that you can use.

While the listing isn’t specific, keep in mind that any built-in USB port is connected to a root hub, and will therefore provide 500mA of power – enough for almost all devices.

What happens if you plug a device that requires more than 100mA of power into a self-powered hub that becomes disconnected from its AC power supply? At that point, the hub becomes a bus-powered hub, the voltage per port drops to 100mA, and, if you have a flash drive plugged into the port, you might destroy it.

To avoid disaster, consider this advice:

-    Think twice before using a bus-powered hub.

-    If you use a bus-powered hub, make sure you know the current requirements for all USB devices you plan to use with the hub. Any device that requires more than 100mA of current will not work with a bus-powered hub.

-    If you’re worried about forgetting to check current requirements before you plug in a new device, use a self-powered hub.

-    If you already have a bus-powered hub and are frustrated because some devices will not work with it, replace it or connect the hub to a compatible AC adapter.

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Hubs and USB Performance Problems

Most, but not all, USB generic hubs sold today support USB 2.0 speeds – but there are innumerable USB 1.1-only hubs still in use. If you plug a USB 2.0 device into a USB 1.1 hub, you will see the same “This device can perform faster” error message you would see if you had plugged the device into a USB 1.1 port on the computer.

How can you tell how fast a USB hub will run? There are two methods I use:

-    Check for markings on the hub

-    Check the properties sheet for the hub

Most USB 2.0 hubs are labeled as such. However, an unlabeled hub might also support USB 2.0 speeds.

To determine the speeds supported by a USB hub, follow this procedure:

1. Plug a USB 2.0 device, such as a storage device or wireless adapter, into one of the ports on the hub.

2. Open Device Manager.

3. Expand the Universal Serial Bus Controllers category.

4. Open the properties sheet for the hub.

5. Open the Power tab and look for the device you connected in Step 1.

6. Repeat steps 4-5 until you find the correct hub.

7. Open the Advanced tab and note the hub’s performance level. A hub that supports USB 2.0 speeds will run at high-speed. A hub that supports only USB 1.1 speeds will run at full-speed.

Note that some desktops with front-mounted USB ports run these ports in USB 1.1 mode only.

USB Hub and Device Power Management Problems and Solutions

By default, USB root and generic hubs are configured to enable the PC to turn off the device automatically to save power. However, USB devices are configured by default to enable the device to wake up the system.

If your system cannot be awakened from standby, check these settings, as well as the power management settings in the system BIOS.

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Cables and USB Device Compatibility

USB cables not made for high-power (over 100mA) devices can cause those devices to fail. Typically, thicker cables (such as the white cable shown below) use 28AWG cable, which is capable of carrying full power to any USB device, while thinner cables (such as the gray one shown below) use thinner cable of unspecified gauge. Smaller-gauge cable prevents full power transmission to the device.

While using an underperforming USB cable won’t cause the device to be damaged, it can be frustrating to need an extension or other cable doesn’t work with some devices.

The second factor is the rise of alternative device cable connections. At one time, virtually all USB devices, with the exception of digital cameras, used the standard B cable connector. With most current devices, except for printers, the standard B connector has been replaced by the five-pin mini-B cable. And, some devices use four-pin mini-B cables or Mini-A cables. To be prepared for any eventuality, consider keeping a universal USB 2.0 cable handy (like the one in the photo below).

The third factor is the need to exceed 500mA at startup with some portable USB hard disk drives. Some onboard USB ports are capable of proving more current to spin up these drives, while others are not. Keep in mind that self-powered generic hubs typically cannot provide additional power for these drives.

If you cannot use a single USB cable to provide sufficient power with some systems, use a double-headed cable. One connector provides power and data services from a single USB port, while the other provides additional power from a second USB port. Some portable hard disk vendors supply this type of cable, while others make it an extra-cost option.

USB Driver Problems and Solutions

Because recent versions of Windows recognize standard USB devices such as mice, keyboards, and storage devices without the need to install drivers, it’s easy to forget that a plug-and-play installation is possible only when the computer has the appropriate driver already installed.

If you plug a USB device into a computer that does not already have the appropriate drivers installed, you will be prompted to run the Found New Hardware Wizard.

Continue only if the installation instructions for the device recommend doing so. In most cases, however, you need to run the device installation program provided on the device’s driver CD before Windows can install the device. In such cases, click Cancel, disconnect the device, and install the driver for the device first.

Once the device is installed, you might be able to update the drivers with the device’s Driver tab on the properties sheet in Device Manager.

Conclusion

Want to avoid having USB problems at all? Here are some best practices that you should follow to get your ports in order.

-    Make sure your computer is configured to run USB ports in USB 2.0 mode

-    Upgrade systems running original Windows XP to SP1 or greater

-    Avoid using bus-powered USB hubs with most bus-powered peripherals other than mice, keyboards, and some types of game controllers

-    Avoid using USB 1.1-compatible hubs with USB 2.0 devices such as storage, printer, scanner, and multifunction devices

-    Use the Device Manager properties sheets for USB ports and devices to solve problems

-    Make sure you install driver software for new USB devices before you connect them to your system

-    Replace USB cables not designed for high-powered devices with thicker USB 2.0-compliant cables

-    Check power management settings in BIOS and Device Manager for USB ports and devices

Mark Edward Soper is the co-author of the new book CompTIA A+ 220-701 220-702 Cert Guide, with Scott Mueller and David L. Prowse (Pearson).

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