| Can I use two video cards in the same system? |
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| There are several ways to do this. You may have heard that it's only possible if one of them is the old Hercules monochrome card, but other options have been available for several years. It is being widely reported that "Windows 97" (or whatever they end up calling it) will include dual-monitor support, using any two PCI video cards. This will be slower than other methods due to the complexity involved. Apparently this will also appear in some future version of NT. The reason this is possible is that the PCI bus allows the cards to map themselves onto different addresses and interrupts, avoiding the built-in conflicts of earlier fixed-address designs. You will have to disable "VGA emulation" on all but one of the cards, and this may not be possible on some cards (one VGA card is still needed to boot the system). A few PCI video cards already have special drivers available that allow more than one (identical) card to be used at once. The Matrox Millenium is often mentioned for Win95, and a few others have drivers for NT (usually aimed at the high-end CAD or DTP markets). Several companies make special video cards that contain two (or four) VGA chipsets, so that several monitors can be attatched to one card. These also usually allow for more than one card to be used at once-- in one case up to 16 monitors using 4 cards! ISA, VLB, and PCI cards are available. They cost more than two regular cards (especially if you're adding to a system that already has one card), but they should run faster and they come with more sophisticated control software. These are the manufacturers I'm aware of: Appian Graphics, Colorgraphics, STB, Tridium DuoGraphics, Diamond Multimedia, Datapath and Miro. To view product information use your WWW browser to access their sites - pointers are available at: http://www.heartlab.rri.uwo.ca/vidfaq/vendors.html For Linux (and other unix variants) there are commercial X servers that support multiple PCI video cards, from Metrolink (MetroX) and Xi Graphics (Xinside). Xfree86 does not support multiple monitors at this time, unless one of them is the old Hercules mono card. Pointers to these sites are available at the web page above. There is also a program called x2x which allows the keyboard and mouse from one X display to control another X display (eg, an X terminal or another computer). See: ftp://gatekeeper.dec.com/pub/DEC/SRC/x2x/ The original PC design used separate address spaces for the CGA (color) and MDA (monochrome) cards, and both could be installed at once, although DOS will only use one at a time (switch with the MODE command). The Hercules monochrome card used the same address space as the MDA card, and all subsequent color cards have used the same address space as CGA, which means they don't conflict with the Hercules card but do conflict with each other (until the PCI bus came along and changed that). Debuggers and CAD programs and often took advantage of this by including support for displaying information on both monitors at once. This still works if your application supports it, but there are a couple of catches. First, the Hercules mono card and all of its clones are 8-bit cards, and they require the other card to be in 8-bit mode also (you may have to set a jumper for this, or it may auto-detect). 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 (computer stores often use them for their demo monitors). See "How can I hook more than one monitor to my video card?" |
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