02 Can I use two video cards in the same system?
Description
This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
02 Can I use two video cards in the same system?
[From: rbean@execpc.com (Ron Bean)]
The PCI bus has made this easier than it used to be, because it allows multiple VGA cards to co-exist in one machine. You need a special driver to let Windows see them as a single display, and since the drivers come from the video card's manufacturer, that means that all the cards must be identical (the Matrox Millenium has been mentioned as one, but there may be others). All of the cards except one must have VGA emulation turned off (the system needs one VGA card to boot, but more than one would cause conflicts).
There are also video cards that have more than one VGA chipset and come with special drivers that make them behave like a single VGA card, but they may be expensive and hard to find. Brands that have been mentioned include STB, Colorgraphics, and Appian Graphics. Check card models listed in the Chipsets List (distributed with this FAQ) for multiple (usually 2 or 4) monitor support.
If you're running X windows, there is a program called x2x which allows the keyboard and mouse from one X display to control another X display. See ftp://gatekeeper.dec.com/pub/DEC/SRC/x2x/x2x-1.24.tar.gz
In the past, the only way to use multiple monitors was to use one Hercules-type monochrome card and one color card (CGA, EGA, or VGA), because the color cards all used the same address space. Most DOS software will only use one at a time (you can switch between them with the 'mode' command), but debuggers and CAD programs often support this type of dual-display system. You may have to change a setting on your VGA card to make it run in 8-bit mode in order for this to work. Note also that many cheap clone monochrome cards include CGA emulation, and there may be no way to disable it.
Windows 3.x can also be set up this way. Include the line DualDisplay=TRUE (or ON) in your SYSTEM.INI file, in the 386enh section. If you open a DOS shell window and type MODE MONO, the shell will appear on the monochrome monitor (I don't know if this still works in Win95).
If you just want to display the same image on several monitors, there are (expensive) signal splitters that will do this (try vendors that specialize in things like cables and switchboxes). Signal splitters for EGA/CGA are somewhat cheaper. See "How can I hook more than one monitor to my video card?"
Continue to:
My Books
