Letting Plug and Play Find New Hardware | Running Microsoft Windows 2000 Professional

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Traditionally, the act of adding a new device has been an exercise in frustration for many personal computer users, as well as a heavy expense for corporate support departments.

Hardware devices typically compete for a limited number of input/output (I/O) addresses, memory addresses, interrupt request (IRQ) lines, and direct memory access (DMA) channels. For your system to work properly, all of its pieces have to dance together without stepping on each other's toes. If your new sound card wants the same interrupt request line as your existing network adapter, something's got to give.

Until recently, resolving a conflict of this kind had entailed some combination of the following: determining which resource was in contention, finding a nonconflicting alternative setting for one of the conflicting devices, making a physical adjustment to the hardware (moving a jumper, for example), and modifying some aspect of the software that used the new device.

To alleviate these difficulties, Microsoft and other computer-industry firms developed the Plug and Play specification. Plug and Play, as its name implies, is intended to make adding a new device to your computer as painless as "installing" a new toaster in your kitchen. Plug and Play has evolved considerably since its initial appearance in Windows 95 so that it's now part of a comprehensive approach to device configuration and power management.

The full realization of this goal requires Plug and Play support from four elements of your system:

The BIOS (basic input/output system). Full Plug and Play support in Windows 2000 requires an Advanced Configuration and Power Interface (ACPI)_compliant system board and BIOS. (The BIOS, routines that manage the transfer of information between system components, is built into the computer's read-only memory, or ROM.) Most new computers (circa 1998 and later) have an ACPI BIOS.

TIP
How to Tell Whether Your Computer Has an ACPI BIOS
To find out whether your computer is ACPI compliant, right-click My Computer and choose Properties. Click the Hardware tab and then click Device Manager. In Device Manager, expand the Computer entry. If your computer has a compatible ACPI BIOS, the expanded entry reads Advanced Configuration And Power Interface (ACPI) PC.

NOTE
Unlike Windows 95, Windows 2000 does not use an Advanced Power Management (APM) BIOS or a Plug and Play BIOS for Plug and Play support. If you have one of these systems (common in 1995–98 models), you should be sure that your computer's BIOS setting for Plug and Play OS is set to No. (See your computer's documentation for information on using its system setup program for changing BIOS settings.)

The operating system. Windows 2000, naturally!

The devices you want to install. Most peripheral devices sold these days are also Plug and Play compliant.

The drivers for those devices. A driver is a software component that controls interaction between the operating system and the device. Drivers for many devices are included on the Windows 2000 CD. If the Windows CD doesn't have the driver you need, you should be able to get a driver from the device manufacturer—either in the box with the device or from the manufacturer's Web site. Most new drivers—even for some non-Plug and Play devices—are Plug and Play compliant. (A Plug and Play driver for a non-Plug and Play device can provide some Plug and Play capability, such as resource allocation and power management.)

NOTE
Windows 2000 supports legacy Windows NT drivers, but these drivers have no Plug and Play or power management capabilities.

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Get Updated Drivers
Even a device that you buy today might have a newer, better driver available. Check the manufacturer's Web site and Microsoft's Windows Update site (windowsupdate.microsoft.com) for new versions—and look specifically for Windows 2000 (not Windows NT) drivers, which likely provide Plug and Play support. For more information, see "Updating a Driver."

With all four elements in place, a newly installed hardware device announces its presence and resource requirements to the operating system. If necessary, the operating system restructures resource assignments on the fly (without requiring you to turn your computer off) to eliminate conflicts. The operating system then broadcasts a message to any running programs, letting them know about the change in your hardware setup so that they can take advantage of any new features.

If a device is removed, the operating system hears about it from the BIOS and informs programs so that they can make any appropriate adjustments. Plug and Play also interacts with power management so that certain devices can be put to sleep when they're not being used and awakened as needed.

So, for example, a Plug and Play laptop computer that supports "hot-docking" can be connected to or disconnected from the docking station without first being turned off. If the docking station has access to a local or network printer, your programs will immediately be informed about any fonts or other resources offered by the printer, and you can begin printing any jobs that you have queued offline.

WARNING
Even if your computer has an ACPI BIOS, always turn off the computer and any connected peripherals (monitor, printer, and so on) before adding or removing any device inside the system.

Provided a new device doesn't present an unresolvable resource conflict, the act of adding Plug and Play hardware and drivers to an ACPI computer running Windows 2000 should indeed be toaster-transparent. And if an unresolvable conflict does arise, Windows identifies it for you so that at least you'll know what options you have.

SEE ALSO
For information about resolving hardware conflicts, see "Troubleshooting a Device That Isn't Working Properly."

With a legacy computer (one that does not use an ACPI BIOS), Plug and Play still offers significant benefits, particularly if you're installing or removing a Plug and Play device. By using the Add/Remove Hardware Wizard (see "Installing a Legacy Device"), you can make Windows aware that a new device is present. If the device supports Plug and Play, Windows can determine which type of device it is and what resources it requires. By consulting the registry (where current resource assignments for all your hardware are recorded), Windows can determine whether the new device's default assignments create any conflicts. If a conflict exists, Windows can make adjustments to the new device (or another Plug and Play device already attached) to avoid the conflict.

When you attach a legacy device, Windows can't adjust the new device's chosen settings, but if some of your other devices support Plug and Play, it might be able to adjust their settings to eliminate conflicts. If not, and if conflicts exist, Windows advises you. You might then have to reset one or more jumpers on the device yourself.