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Chapter 4
144
Managing and Troubleshooting Device
Conflicts
You can configure, diagnose, and modify settings for hardware devices using
the Device Manager.
For example, each resource assigned to a device—a memory address range,
interrupt request (IRQ), I/O port, Direct Memory Access (DMA) channel,
and so on—must be unique or the device will not function properly. For PnP
devices, Windows XP attempts automatically to ensure that these resources
are configured uniquely. When a device has a resource conflict or is not
working properly, Windows displays a yellow circle with an exclamation
point next to the device’s name. If a device has been improperly installed or
if it’s been disabled, Windows displays a red X next to the device name in
Device Manager.
If you are having trouble with a particular device, sometimes it’s helpful to simply
uninstall the device’s driver, reboot the computer, and then attempt to reinstall the
driver. Because PnP devices automatically invoke an installation procedure, if
you do not want the operating system to try to install a particular device when-
ever the computer restarts, disable the device rather than uninstall its
driver.
Occasionally, two devices require and can share the same resources; this does
not always result in a device conflict—especially if the devices are PnP-com-
pliant. Sometimes, two or more devices can share resources, such as inter-
rupts on Peripheral Connection Interface (PCI) devices. It all depends on the
drivers and the computer. For example, Windows XP might share IRQ 9 or
IRQ 10 among multiple PCI devices, such as USB host controllers, SCSI
adapters, and audio controllers. In many instances, you cannot change
resource settings for PnP devices because no other settings are available.
When you install a non-PnP device, the resource settings for the device are
not configured automatically. In some cases, you might have to manually
configure these settings. Such a configuration is called forced hardware, and
the System Information Utility (
msinfo32.exe) lists them under System
Summary, Hardware Resources, Forced Hardware.
The appropriate range of resource settings should appear in the device’s user
manual. If you need to change resource settings for a device, follow these
steps:
1. Open Device Manager and expand the device category where the
device is located.
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Setting Up and Troubleshooting Hardware Components and Device Drivers
145
2.
Right-click the device for which you want to adjust its resource settings
and select Properties.
3. Click the Resources tab and clear the Use Automatic Settings check
box (if available). If the Use Automatic Settings check box is dim
(unavailable), you cannot change the resource settings for this device.
4. Choose one of the following courses of action:
Click the Settings Based on drop-down list box to select from the
predefined list of settings.
Click a Resource Type item shown in the Resource Settings list box
and then click the Change Setting button (see Figure 4.5) to indi-
vidually modify the resource’s setting. Change the setting and click
OK. Repeat this action for each resource setting that you want to
change.
5. Click OK for the device’s properties sheet to return to the Device
Manager window.
Generally, you should not change resource settings manually because when you do
so, the settings become static and Windows XP has less flexibility when allocating
resources dynamically to other devices. If too many resource settings are static,
Windows XP might not be able to install new PnP devices. In addition, if you manu-
ally change resource settings to incompatible values, the device might lose function-
ality.
Figure 4.5 Adjusting resource settings for a device, such as COM1.

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