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Multiple Monitor Guide

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Multiple monitors let you extend your Windows desktop across more than 1 monitor for extra screen real estate.

  1. O/S & Hardware Requirements
  2. Advantages
  3. Disadvantages
  4. Getting Started
  5. Setting the Primary Display
  6. Issues and Annoyances
  7. Multi-monitor Video Cards
  8. Multi-monitor Displays
  9. Developer Resources
  10. Other Sites

O/S & Hardware Requirements

  • Supported natively by Windows 98/Me/2000/XP (Mac users have had multi-monitor support from almost day one).

  • Each monitor must have its own video card (i.e. 3 monitors would require 3 video cards). The exception being if you have special multi-monitor video cards.

  • Whether or not the primary or secondary displays can consist of traditional (CRT) monitors or (LCD) flat-panel displays is video card dependent. Most new graphics cards will have models which support flat-panel displays either by default or through the use of an add-on adapter.

  • All display adapters must be either PCI or AGP (ISA/EISA/VESA is not supported).

  • Some video card manufacturers support multiple displays on Windows 95 & NT 4.0 with specialized drivers (this guide discusses multi-monitor support as implemented in Windows 98 and above).

  • Virtually any adapter can be used for the primary display (on-board adapters may cause some problems). Additional adapters require specific driver support.

  • Anywhere from 2 - 9 monitors are supported.
  • The Good

  • Each monitor can be set at its own colour depth and screen resolution.

  • Windows lets you specify the position of each monitor with respect to one another.
  • The Bad

  • Full-screen mode (DOS sessions or DirectX applications) are always locked to the primary monitor. For example, Microsoft Flight Simulator has multi-monitor support, but secondary display views must be in windowed mode. Hopefully future versions of DirectX will solve this dilemma.

  • Not all secondary display drivers support DirectDraw or Direct3D.

  • Running multiple displays results in a slight performance hit on your system, depending on what you're doing. Cool Computing has a good review on this.

    Getting Started

  • The Windows 98 display.txt file has some preliminary information regarding basic setup and troubleshooting for multiple monitors.

  • Some common chipsets are supported as secondary displays right from the Windows CD (as outlined in the display.txt file). If your card is not directly supported by Windows, check with your video card manufacturer for an update. Virtually every manufacturer has multi-monitor compliant drivers available from their web site.
  • Setting the Primary Display

  • The primary display is set by the order in which the display adapters are initialized by the system BIOS.

  • If all adapters are PCI, then you can just switch the order in which you place the cards in the slots on your motherboard.

  • Most BIOS's initialize PCI adapters before AGP adapters, meaning that your AGP adapter will default to a secondary display. Contact your motherboard manufacturer for an updated BIOS that will allow you to configure the order in which your AGP adapter is initialized to set it as the primary display.

  • If your display adapter allows you to disable the VGA BIOS on the card, then it will automatically default to a secondary display.

  • In Windows 2000/XP, primary and secondary displays can be set through software.
  • Issues and Annoyances

  • In order that 'legacy' applications are not crippled on multi-monitor systems, Windows reports only the dimensions of the primary display by default. Otherwise, applications would maximize or center themselves across both monitors. Specific system APIs (introduced in Windows 98 and above) allow new applications to exploit multiple monitors.

  • Since many applications are not multi-monitor aware, many dialog boxes and dockable toolbars will always default to the primary display.

  • Some TV Tuners will only work on the primary display (perhaps due to the lack of DirectDraw support on some secondary display drivers).

  • Placing monitors too closely to each other sometimes causes interference between them. Microsoft has an article about this in their knowledge base (along with recommended solutions).

  • Desktop wallpaper cannot be customized with respect to each monitor. However, Brett Foster has details of a workaround on his site.

  • Screen capturing is extended across all displays.
  • Multi-monitor Video Cards

  • Many manufacturers have released multi-monitor video cards (which support > 1 monitor) as a single slot solution. Depending on the product, these cards come in a dual or quad configuration, either as PCI or AGP card. Some of these cards even have legacy drivers for Windows 95 or NT 4.0. Each product has a different moniker for its multi-monitor management software.

  • Note - Windows 2000 does not fully support multiple displays from a single graphics card. Some cards have updated drivers that work around this problem, but you may encounter problems such as windows being extended across both monitors, inability to set independent screen resolutions or colour depths etc. Windows XP resolves this problem with a feature called Dualview.
  • Multi-monitor Displays

  • Many variants of integrated multi-monitor LCDs also exist, supporting several flat panel displays in different configurations and mounting options:

  • Developers Resources

  • How to Exploit Multiple Monitors (Microsoft Systems Journal - June 1997)
  • multimon.h is required to use any of the new APIs and is available in the Microsoft Platform SDK.
  • Other Resources

  • Multi-Monitor Resources (
  • Multiple (sponsored by 9X Media)
  • microsoft.public.win98.display.multi_monitor newsgroup
  • Last updated March 10, 2002