By Karen Kenworthy
DMA, IRQ, I/O, UMB. Ever feel like you're drowning in a sea of alphabet soup? Where's a lifeguard when you need one?
Don't panic--Windows' Device Manager is coming to the rescue. It may not be as sexy as those Baywatch hardbodies, but it can still save your assets.
You've probably noticed your modem lights blinking and your printer being reset each time Windows 95 loads. All this activity is caused by Windows' Plug and Play (PnP) software. PnP scans your PC, probing every device and circuit it finds. Along the way, it configures those devices it can, and makes a detailed record of your computer's complete hardware configuration.
Most of this hardware management goes on behind the scenes, without human intervention. But Device Manager provides a way for you to wade in when necessary. It also gives you access to Win95's treasure trove of configuration information.
Displaying Device Manager's main window is easy. Right-click on the My Computer icon on your Desktop and select Properties from the Context menu. Or double-click on the System icon in Control Panel. Either way, when the System Properties dialog appears, select the Device Manager tab.
Device Manager's main window gives you two quick peeks at your hardware configuration: View Devices by Type and View Devices by Connection. Clicking on the appropriate radio button changes the view. But the key to Device Manager's real power lies in the buttons at the bottom of the window.
Device Manager reveals what Windows learns during the startup hardware probe in several ways. My favorites are the Resource Summary Report and System Resource Report. These two printed reports tell you all you want to know about your computer's hardware configuration and more. To print either, click on Device Manager's Print button, then provide the information requested in the resulting dialog box.
The Resource Summary Report (called System Summary in Device Manager's Print dialog) usually runs about two pages and consists of five sections. The System Summary section tells you the type of CPU, BIOS and bus your computer uses. It also reports the version of Windows and BIOS you're running, and who built and owns the computer.
The IRQ Summary section lists all IRQ (interrupt request) lines present on your computer and tells how each is used. The IO Port Summary lists all I/O ports used by an adapter card or any part of your motherboard's circuitry. Similarly, the Upper Memory Usage Summary section displays all ranges of your computer's upper memory region (memory addresses between 640KB and 1MB) that are in use. The last section of the report, the DMA Usage Summary, lists all DMA (direct memory access) channels your current hardware configuration is using.
The System Resource Report (called All Devices and System Summary in Device Manager's Print dialog) is a much more detailed account of your computer's hardware configuration. It's often a dozen or more pages and begins with the same five sections that appear in the Resource Summary Report.
But that's just the beginning. The System Resource Report details your computer's disk drive configurations (size of each drive including the number of cylinders, heads and sectors per track), all detected adapter cards and motherboard device circuitry (serial and parallel ports, network interface cards, SCSI and IDE adapters, video adapters, mouse ports and so on), and the peripheral devices attached to those circuits (monitors, mice, CD-ROM drives, modems, keyboards and so on).
The report also includes hardware resources such as IRQ lines and DMA channels, plus the drivers used to support each item. Driver information includes the size of the driver file, the author of the driver and any version information available.
Win95's Startup probe is clever. In most cases, it will find all the adapters and other motherboard circuits you knew about, and a few more besides. It's also good at deducing the hardware resources each device or circuit requires.
But sometimes, Windows misses a device. When this happens, the OS presumes the hardware resources used by the overlooked device are still available, and it may inadvertently assign them to some other device. To prevent this from happening, Device Manager allows you to manually reserve hardware resources, keeping Windows from reassigning them.
To do so, select the first item in Device Manager's list of devices (Computer), click on the Properties button and select the Reserve Resources tab. The resulting dialog box lets you reserve four types of resources: IRQ lines, I/O ports, DMA channels and memory addresses. Once you've selected a resource type via the dialog's radio buttons, you'll see a list of resources already manually reserved. To add to the list, click on the dialog's Add button, then supply the requested information. To modify or delete a resource you've previously added, select the resource from the list, then click on the Modify or Remove button.
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Know Thy Hardware Configuration
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Give Your Hardware a New Profile
Device Manager has another nifty trick up its sleeve. It allows you to create more than one hardware configuration, then choose among them each time Win95 starts. For instance, one configuration could include a network adapter card; another could disable that device.
Windows calls each hardware configuration a Hardware Profile. You can create a new one by cloning an existing profile and then enabling and disabling devices in the new profile. To clone an existing profile, first select the Hardware Profiles tab in the System Properties dialog. From the resulting window, select the existing configuration you wish to clone, then click on the Copy button. Name the new profile, and you're done.
Now you're ready to customize the new profile. Go back to the Device Manager tab and select a device you want to disable or enable in the new configuration. When the device's Properties dialog appears, select its General tab.
If the dialog box doesn't contain a Device Usage section, you can't disable the device. If it does contain this section, you'll see a list of your computer's Hardware Profiles, with a check box beside each one. A mark in a check box indicates the device will be enabled when the corresponding profile is in effect. Clearing the box disables the device when the computer is running under that profile.
You'll see the effects of these changes the next time your computer boots. While the computer is still in text mode, a short menu will appear, allowing you to choose either your computer's Original Configuration profile or one of the new ones you've defined.
Device Manager also allows you to remove a device. To do this, go back to the Device Manager tab. Choose the device you wish to remove from the list and click on the Remove button.
Beware of one big gotcha, however. The next time you start Windows, its PnP software may re-detect your "removed" device and automatically reinstall it. If that happens, the only way to disable the device permanently (short of physically removing it from your PC) is to modify each of your Hardware Profiles, disabling the device within each one.
Hardware upgrades often require swimming far from shore. Nothing makes the process perfectly safe or easy yet, but Device Manager and PnP are a big help. Now, if they just looked better in a bathing suit.
Contributing Editor Karen Kenworthy is the author of Visual Basic for Applications, Revealed! (Prima Publishing, 1994) and the manager of WINDOWS Magazine's forums on America Online and CompuServe. Contact Karen in the "Power Windows" topic of these areas. To find her E-Mail ID Click Here