Although PCI, AGP, and PCI Express cards and integrated devices are designed to share IRQs, you may see a resource conflict when you attempt to install a legacy port, such as a serial (communications) or parallel (LPT) port.
When a hardware conflict is detected, it's reported by the wizard at the end of the device installation process.
If you cannot select a nonconflicting setting with the device you're installing, you have a few options:
• Change the settings for the conflicting device with the Device Manager, as discussed later in this chapter.
• If the device you are attempting to install is an integrated legacy port, restart the system and select different settings in the BIOS setup. With a modern system, select Auto as the setting, which will enable the BIOS or Windows 7 to select a nonconflicting setting. If you must choose a particular IRQ or other hardware resource setting, make sure you don't choose a setting used by another port or card. For example, it's easy in most systems to choose the same IRQ and I/O port address range for both serial (communications) ports, causing a conflict. Be sure you choose different IRQs for each serial port.
In general, be cautious about configuring resource settings manually. When you change settings manually, the settings become fixed, and Windows 7's built-in device contention resolution is less likely to work. Also, if you install too many devices with manually configured settings, you might not be able to install new PnP devices because none will be available. In the worst-case scenario, the system might not even boot if conflicts occur with primary hardware devices, such as hard disk controllers or video cards. If you decide to use manual configuration, make sure you know what you're doing and have the specs for the hardware in question at hand.
• In some cases, particularly with legacy ports, you may not be able to resolve a conflict and will need to disable the conflicting device on one of the cards with the Device Manager.
If you have a resource conflict, what should you do? Most drivers don't have resources that can be reassigned. Others have an option button called Reinstall Driver that's useful if the system thinks that would solve a nonfunctioning-device problem. Most PCI, PCI Express, and AGP cards (as well as integrated ports such as USB, FireWire, and PATA/SATA) don't permit their resources to be reassigned because they obtain their resource settings from Windows or from the system BIOS. Some systems allocate resources depending on which slot you use for a particular card.
However, you can usually reassign resources for legacy ports like serial (COM) and parallel (LPT) ports. To reassign a resource, open the Device Manager, open the Properties dialog box for the device, and click the Resources tab. To select a different resource, uncheck the Use Automatic Settings box and choose Change Setting.
The Windows 7 Control Panel
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