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    Guide to Dual Monitors in Windows


by Drew Dunn

One of the reasons that computers are getting cheaper is because monitors are getting cheaper. The video hardware that drives them is also more affordable than ever before. Microsoft realized that when they released Windows 98 and built in support for multiple monitors. That support continued with 98SE, 2000 and ME. If you use NT, you're not out of luck, but this article won't help you. Your best alternative is to use a dual headed card, like the Matrox G450, one with two monitor outputs.

Getting dual monitors to work correctly seems to be a hit or miss affair. In many cases, it's just a matter adding a second video card and monitor and rebooting the computer. In other cases, you need to do some cyber gymnastics to get things working correctly.

The process is the same no matter which version of Windows you are using. First, be sure that your system is working correctly. Boot into safe mode and verify that you have only one video adapter and monitor showing in the Device Manager. If there are more, but you only have one adapter and monitor, you'll need to remove the extras.

Once you're sure that your video setup is working fine, turn off the system and look inside. Remember that you'll need a video card for each monitor that you plan to run under Windows. That means that your system must have a free expansion slot for each one. You may find that you have problems with IRQ sharing or DMA channels, depending on your motherboard and video card, although many video cards seem relatively intolerant of IRQ and DMA conflicts. Install your video card in the appropriate slot, and then connect the monitor.

Restart your system. If all goes well, your computer will boot the same way that it always has…the second monitor will still be dark. If your system prompts you to login, do it. You may need to install drivers for your second video card, depending upon whether or not Windows has built in drivers or not. Just follow the on-screen instructions.

Once the drivers are installed, check the Device Manager to make sure that the display adapter is properly detected:


Once the drivers are installed, open the Display Properties window. In the settings screen, you should see something like this:

You'll see that a second display is shown. Click on the grayed out display marked as "2". The window will change slightly to look like this:

You can then change the desktop resolution and color depth. Once you've done that, click your mouse on the "Extend my Windows desktop onto this monitor" to enable it. Remember that the resolution, color depth and refresh rates of each monitor adapter combination don't have to be the same. The window should look something like this now:

Click on OK and your second monitor should activate itself as an extension of the first:

You'll find that you can change the relative geometries of the two monitors by moving their respective boxes around in the Settings window.

What if things don't work?

If you can't get your second monitor to work at all, there are a couple of steps that you can take. In some systems, you need to change a BIOS system to allow the PCI display adapter to initialize first, instead of the AGP adapter. You should be sure that both of your display adapters are supported by the version of Windows that you are using.

Also, be sure that the display parameters (resolution, color depth, etc.) are within your monitor's limits. Windows allows you to select different display parameters for each monitor, so even though one might have lower performance than another, you'll still be able to use it.

Windows 2000 driver support for older PCI cards may be a little iffy. Many popular cards do have drivers, but just about as many don't. Also, remember that your computer has only one AGP slot, so you can only use one AGP card. The rest have to be PCI or ISA.

And speaking of ISA video cards, I'd really recommend against using one. You'll find that your video resolution and color depth are very minimal and you may create more problems with IRQ sharing than you want to get into. Also, of course, many newer motherboards don't have ISA slots.

If you have a motherboard with one of Intel's i815 chipsets, you may have onboard AGP video. While it might be tempting to use the built in video and get a separate PCI card for the second display, please let me talk you out of it. Almost any AGP card that you buy, even the cheapest one, will outperform the video from these chipsets. If the onboard video is your main video source, put your money into a new video card before you consider adding a second monitor.

Dual monitor setups are a great way to expand your desktop without buying a monstrously expensive large monitor and, in most cases, it's very easy to do. A little preparation before you do the job should result in a whole lot of fun at the end.

Drew Dunn














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