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Multi-monitor, also called multi-display and multi-head, is the use of multiple physical display devices, such as monitors, televisions, and projectors, in order to increase the area available for computer programs running on a single computer system. The use of two such displays is called dual display, dual screen or dual monitor. Research studies[1][2][3] show that, depending on the type of work, multi-head may increase the productivity by up to 40-50%.


Contemporary windowing systems, such as the X Window System (used by GNU/Linux) and those used by Microsoft Windows and Mac OS, all support simultaneous use of multiple monitors. Multi-monitor support once depended on specialized proprietary video drivers and support from windowing systems and window managers.

Multi-monitor has been a standard feature of Apple's Mac OS since the introduction of the first color Macintosh II in 1987.[4]

Windows 98 (introduced in 1998) was the first version of Microsoft Windows that supported multiple monitor configurations. In 2001, Windows XP added DualView [5] which allows two monitors to host the Windows desktop, while being driven off two separate video outputs of a single display adapter.

Configuration and placement[edit]

Single PC multi-monitor[edit]

A multiple monitor setup increases the net display area of a system and can be an inexpensive way of improving computer usage.[6] The resulting display area after upgrading to a multi-monitor configuration is limited by the size, resolution and number of monitors. The monitors used for multi-monitor can be different types (LCD or CRT) and sizes. The operating system manages the monitors' resolutions independently.

Video output on a computer is generated by a video graphics device, or Graphics Processing Unit (GPU), typically on a removable card but which may also be integrated into the motherboard as a discrete device or as part of the chipset logic. The output is interpreted and displayed by a variety of devices. Video outputs are generally connected to a monitor (of either the CRT or LCD type); however, they are increasingly being connected to projection equipment or television sets. As a result of this trend, manufacturers have produced video cards which can connect to several types of display devices using the appropriate interface. A "Dual Head" configuration utilizes a video card that supports two discrete outputs. Users may also utilize two discrete video cards, and sometimes even an integrated motherboard video socket plus a second video card, though often the motherboard disables the integrated video when a discrete video card is used (a limitation that was common on older chipsets featuring integrated AGP graphics and an AGP upgrade slot).

More than two monitors[edit]

A multi-monitor system for gaming.

Prior to mainstream adoption of the PCIe bus, configurations of more than two monitors were either achieved with an AGP card with dual video outputs or by using an AGP graphics adapter as the primary device and a conventional PCI graphics adapter as a secondary device however, given the bandwidth limitations of the older PCI bus,[7] such setups were not common, and maximum overall graphics performance could be obtained only by using specialty solutions such as the Matrox G450,[8] which features four outputs from one graphics adapter. Now that computers with two or more PCIe interfaces are popular, middle- and high-end computers are no longer limited to two monitors driven by a single main graphics adapter. If a dual PCIe interface is not available or is otherwise occupied, a standard PCI graphics card can still be used to provide additional video outputs, albeit with performance trade-offs[citation needed]. Specialized application environments such as CAD, day trading of corporate stocks, and software development are increasingly using six or more monitors on one production system.[citation needed] Multi-monitor gaming/simulation is also becoming more common; however, the hardware expense can be a limiting factor.[9]

Additional monitors can also be connected to PCs via a USB connection such as DisplayLink.

Multiple PC multi-monitor[edit]

Software such as Maxivista for Windows and ScreenRecycler for Mac OS X let one set up multiple PC multi-monitor mode through virtual display drivers and client-side software. Similarly, software such as InputDirector or Synergy allows one to use multiple PCs, each with their own monitor or monitors, and transition from one to the other on screen edges as if they were one machine. This allows each machine to be doing a different task, freeing up resources.

Linux users may use Xdmx, which is an X Window proxy. It is possible to have multiple monitors displaying as a single virtual desktop. Multiple university display wall projects use this capability,[10] such as The LambdaVision display by the University of Illinois at Chicago's Electronic Visualization Laboratory, with 55 LCD monitors which are connected to 32 PCs.[11] This results in a 17600 x 6000 pixel display. As long as the xinerama extension is enabled, GNOME can use the entire desktop.

An additional and different approach to multiple monitor systems involves using the monitors of networked computers to display the output of a central computer. By using the graphic cards of the networked computers, stability and speed are dramatically enhanced. This is often a preferred choice for systems in which adding additional graphics cards is problematic, such as laptops.

The additional monitors can be extensions of the desktop or mirrors of the central display. The arrangement of these monitors can be configured within the properties tab in the windows display dialog box, making horizontal, vertical, or other monitor configurations possible. Further, because the additional monitors are powered by networked computers, they can be located wherever the network reaches, both wireless and hardwired.

Display modes[edit]

Clone mode[edit]

Since before personal computers existed, video signals have been split with simple Y-adapters to provide duplicate signals to multiple monitors for various reasons. When personal computers came to have video outputs, this naturally carried over—sometimes for the purpose of presentation, and sometimes to provide a different representation of the same output (for example color alongside the higher resolution monochrome interpretation of the output of an Apple II). Later systems—particularly portable machines with built-in displays—provided built-in redundant outputs for this. Even later systems, in addition to being capable of the discrete modes described below, are able to mimic this "cloning" or "mirroring" behavior (typically defaulting to it upon power-up/reset).


In the early days of the IBM Personal Computer and its clones, there were two main types of display adapter: color (CGA, EGA) and monochrome (MGA). Since these devices used fixed areas of the 1 MiB address space of the 8086/8088 CPU, it was not possible to have more than one of the same type in a machine. However, since color adapters used a different space than monochrome, one of each could coexist. This led to systems using a CGA or EGA for color graphics, and an MGA for monochrome text, on side-by-side monitors.

The Commodore 128 was capable of similar behavior using its C64 compatible 40-column output for graphics on one monitor, alongside its 80-column capable output on another.

Span or extended desktop mode[edit]

Most[clarification needed]—if not all—current multi-head video cards are able to "span" a single frame buffer across two monitors. The result is one large rectangular desktop space, of double either the horizontal or vertical resolution. (For example, when two 1024×768 displays are used, they can have a combined virtual resolution of either 2048×768 or 1024×1536.) Both monitors operate at the same resolution and depth settings, and usually the same refresh rate.

In "extended" mode, additional desktop area is created by giving each monitor its own frame buffer. The result is a virtual desktop space comprising multiple adjacent, but not necessarily aligned, rectangular areas. In this considerably more flexible configuration, each monitor can be of different resolution, depth, and refresh rate; and the desktop area is not necessarily rectangular. This mode is actually older than spanning—first appearing in 1986, when Radius introduced the vertical Full Page Display for the Macintosh Plus (which was a dramatic increase over the machine's 9" built-in display).

Both of these modes present the display space to the user as a contiguous area, allowing objects to be moved between, or even straddled across displays as if they are one.

Some problems occur when a user wants to define one large spanned view of two 1024×768 displays into one 2048x768 display in Windows Vista and Windows 7 since only extended desktop is supported and spanned resolutions are non-existent in many applications such as games and presentation software. Windows XP supports both spanning and extended desktops through older NVidia and ATI drivers.

Hybrid Span mode[edit]

This is a technique that allows using multiple GPUs to create a single unified display, and this is a more modern approach to utilizing multi-monitor displays. The two main companies involved in this market, AMD and nVidia, use the same technique of grouping all monitors together to, in essence, trick the computer into using one large spanned resolution, eliminating the need for special software patches.[12][13] AMD's EyeFinity, or more specifically SLS (Single Large Surface), creates a large, spanned resolution across three and up to six monitors.[14] nVidia's approach to this is called "Surround" and it also creates a large, spanned resolution; however, it only supports three monitors.[15]

Commercial systems[edit]

Major players in the visual computing technologies currently include AMD Graphics (formerly ATI Technologies), which supplies graphics hardware and supports its function via ATI's Hydravision Multi-Monitor Management Software; NVIDIA, also a hardware supplier, which includes software support under the moniker of nView Multi-Display Technology; and Matrox, a third hardware supplier providing both multi-display add-in boards and a series of external multi-display upgrade units known as DualHead2Go and TripleHead2Go. The technology provided by these companies was once limited to the professional graphics market, but has gradually become more widespread and affordable in the consumer market. The latest version of Microsoft Windows supports up to 64 monitors.[citation needed]

There is also a growing movement in multi-monitor displays as production companies around the world are using this technology to expand their screen setups without the extravagant costs included with multi-screen processors. Now with the commercial systems mentioned above in place, bands and other entertainment based events are able to create technological setups with ease and low cost.[16]

Google's Liquid Galaxy uses multiple monitors to create an immersive version of Google Earth.[17]


The primary hardware disadvantage to multi-monitor use is that common resources of the video card are divided between each display's output duties. For example, if a user is showing a 2D widescreen desktop display at 1680x1050 resolution and 32-bit color depth on a second monitor while playing a game on the primary monitor, nearly 7 MB of video memory (VRAM) will be consumed by the second display image, making it unavailable to the game. In some cases, the decreased processing power and VRAM available to each display may lead to unacceptable performance on both devices. When this situation is encountered, the common remedy is to install an additional video adapter and connect the additional display to the new device. Ongoing improvements in graphics technology have minimized this issue in recent years, with many mainstream graphics adapters now supporting 1 GB or more of VRAM and a graphics core purpose-built around two or more video outputs.

Although multi-monitor configurations are increasing in number, single monitor PC users continue to dominate the market. Cost can be one problem for multi-monitor, as there is the cost of the second display and sometimes an additional video adapter as well.

Full-screen software can pose a problem on a multi-monitor configuration. Many full-screen applications make use of the absolute edge of the display to control view movement, and may not work properly on a multi-monitor PC, for example by failing to track the mouse cursor properly when it continues onto the next display of an extended desktop. "Edge-scrolling" can frequently be found in full-screen image viewers, 3D model editors, and real-time strategy (RTS) genre video games. Newer software is more likely to either be multi-monitor aware, or else not depend on the endpoints of the visual area as a fixed reference, albeit this does not solve all of the ergonomic problems a user may encounter.[citation needed]

For example, many full-screen applications, even when tolerant of multi-monitor displays, only cover one display area and relegate the other display to secondary use. This can create edge-scrolling problems when the cursor crosses between the display fields. One notable exception is flight simulator software, which might take over all available displays, e.g. using one display to show a windshield view of the simulated flight and presenting simulated instrumentation and controls on another display.

Problems can also arise if the user clicks outside of the full-screen application's display area—though this is not directly a multi-display problem. Anything that shifts focus (including clicking elsewhere, pressing the Windows/Super key, typing Alt-Tab or Command-Tab, etc.) away from a game, or any full-screen application, can cause grief—even on a single-monitor system. The full-screen application may drop out of full screen mode. A game may continue running, yet control has been taken away, since the newly focused application is now first in line for console input events.

When software is not multi-monitor aware, or the edge-scrolling problem is encountered, the user must adjust his or her computer usage to minimize it, or engage a work-around solution. One of the most common methods of overcoming the edge-scrolling problem is to set up a multi-monitor orientation on a diagonal. The diagonal orientation means there is no adjacent desktop space on any primary edge, generally preventing the mouse cursor from moving beyond the screen edge. As a downside, a diagonal orientation can make moving the mouse from monitor to monitor difficult, as the user must target a very narrow transition region in order to move the cursor between displays. A diagonal orientation also does not usually correspond to the physical arrangement of monitors, reducing the intuitiveness of the crossover point.

Another method is to temporarily disconnect the unused monitor(s). However it is not always desirable to disable all other displays, and on a Windows operating system platform, the OS will generally compensate for missing displays by reorganizing all desktop shortcuts onto the remaining active monitor(s). This can be overcome by using utilities that can store shortcut locations, such as ATT.

There are also some programs that provide full workarounds to the issue. One such utility is CSMMT.[18]

Graphics cards[edit]

These display adapters are built with two or more outputs of various types. Typically these will be DVI ports and/or VGA; however, DisplayPort and HDMI are now very popular. The older CRT monitors will usually use VGA, while higher-end CRTs may include BNC or DVI. LCDs - depending on the model - usually support either or both. Conventional or high-definition television outputs, like DisplayPort and HDMI, are also sometimes provided, although these will commonly disable one of the other display outputs when accessed and cannot be used to create a third display device.

As of 2013, some graphic cards feature as many as four DisplayPort outputs and support that number of independent monitors.[19] Recent versions of Linux and Windows 7 also support multiple graphic cards connected to different monitors.


Another way to extend the number of displays on one computer is to add displays via USB. Starting in 2006, DisplayLink released several chips for USB support on VGA/DVI/LVDS and other interfaces.[20] For "raw" displays with LVDS or TTL interface Display Solution provides driver boards with USB- and even Ethernet interfaces.[citation needed] Under Windows up to 6 USB displays can be connected.[citation needed]

Multi-display setups in the workplace[edit]

Office worker with dual monitors

In many professions, including graphic design, architecture, communications, accounting, engineering and video editing, the idea of two or more monitors being driven from one machine is not a new one. While in the past, it has meant multiple graphics adapters and specialized software, it was common for engineers to have at least two, if not more, displays to enhance productivity.[21]

2×3 display setups are common in financial market making.[citation needed]
Three monitors using shared stand

Multi-display setups are also very common in investment banks, particularly in market making, where they allow the simultaneous display of several screens of prices as reference data, allowing the trader to keep an eye on the market. Setups of 6 displays (2×3: 2 rows of 3) are common on interest rate trading desks[citation needed], which involve many numbers, while 8 displays (2×4: 2 rows of 4) are not uncommon. Financial multi-display setups may also incorporate Bloomberg Terminals, or these may be adjunct to the main display.

Now that multi-monitor setups are more budget-friendly[citation needed], it is not uncommon to see a wide range of business professionals using multiple monitors to increase visual area.[citation needed] This advantage helps promote the concept of a paperless office by increasing the quantity of simultaneous media that can be viewed digitally, although the advantage of viewing two documents simultaneously is also feasible on many larger widescreen monitors.

To save the table space, multiple monitors may be mounted on the shared stand.

Developing software for Multiple Monitor Workstations[edit]

Ordinary software does not need special support for multiple screens even if it uses graphic accelerator. At the usual application level multihead is presented just as a single larger monitor spanning over all screens. However some special approaches may increase the multihead performance.

With multiple monitors present, each screen will have its own graphics buffer. One possible scenario for programming is to present to OpenGL or DirectX a continuous, virtual frame buffer in which the OS or graphics driver writes out to each individual buffer. With some graphics cards, its possible to enable a mode called "horizontal span" which accomplishes this. The OpenGL/DirectX programmer then renders to a very large frame buffer for output. In practice, and with recent cards, this mode is being phased out because it does not make very good use of GPU parallelism, and does not support arbitrary arrangements of monitors (they must all be horizontal). A more recent technique uses the wglShareLists feature of OpenGL to share data across multiple GPUs, and then render to each individual monitor's frame buffer.[22]

Other uses[edit]

Older uses[edit]

From the mid-1980s through 1990s, a popular configuration for software developers was to employ a general-purpose VGA, EGA, or CGA display for managing the program under development and an independent monochrome Hercules or MDA card driving a second monitor for displaying debugging information. Many DOS debugging applications supported this configuation. It was possible to operate two display cards in this fashion, even with operating systems such as MS-DOS which did not support multi-monitor natively, because the Hercules and MDA cards used a different hardware memory address than conventional graphics cards and could operate concurrently without creating hardware conflicts. Modern hardware is not affected by the limitations of earlier systems like these when running modern operating systems, because the hardware and software are both designed such that the operating system can abstract the various hardware devices from each other and then manage them appropriately. The first Macintosh computer to support multiple monitors was the Macintosh II. The Macintosh SE/30, which had one slot in it, also supported a second monitor which could be color even though the main monitor was monochrome.

Interactive television sometimes coordinates the use of a television screen and a computer display.

Arcade machines[edit]

Arcade games were released in the 1980s and 1990s which used a multi-monitor configuration. The earliest of these is the game TX-1, a driving game by Atari from 1983, which used a cockpit cabinet with 3 19" CRT monitors side-by-side to give a wide viewing area. Its successor, TX-1 V8 released in 1984, also used the same 3 monitor configuration. Tatsumi released Buggy Boy in 1985, in both cockpit 3 monitor and upright single monitor cabinets. Darius from 1986 used an upright cabinet which was around half as wide again than a standard arcade cabinet of the time. It used 3 14" FST (flatter squarer tube) monitors but in this case, 2 monitors were mounted on the left and right with the screens pointing upwards and one was mounted in a box at the centre rear of the cabinet, and using a two way mirror a seamless wide image was obtained. A similar effect was seen in Darius II, also known as Sagaia, (which was also released in twin larger monitor format) and The Ninja Warriors.

As arcade technology entered the 1990s larger cabinets were being built which in turn also housed larger monitors - such as the 3 28" screen version of Namco's Ridge Racer from 1993. Although large screen technology such as CRT rear projection was beginning to be used more often, multi-monitor games were still occasionally released, such as Sega's F355 Challenge from 1999 which again used 3 28" monitors for the sit-down cockpit version. The most recent use of a multi-monitor setup in arcades occurred with Taito's Dariusburst: Another Chronicle game, released in Japan in December 2010[23] and worldwide the following year.[24] It uses 2 32" LCD screens and an angled mirror to create a seamless widescreen effect.

Multi-monitor support[edit]

  • OS
    • Microsoft (not official): Virtual Display Manager[25]
    • X Window: Xinerama and XRandR 1.2
    • Matrox: Powerdesk (Windows) / Joined Mode (Multi-card)
    • Nvidia: nView (Windows) / TwinView (FreeBSD, Linux), also multi-card.
    • ATI: HydraVision, Eyefinity
    • Citrix Presentation Server (Citrix ICA Client)
    • Microsoft Terminal Services (RDP Client) value: RemoteApp[26]
    • Multi Display QuadStations -2-12 Displays[27]

Application support[edit]

Games support[edit]

The following games support multiple screens inherently:

Other games such as Guild Wars and World of Warcraft can also be made to run in multi-monitor set-ups, with the addition of third party software to enable the ability, or by running the game in windowed mode and resizing the window.[37] A larger list of games that support dual/multi screen modes is available at WSGF.[38]

  • Star Trek: Armada and Star Trek: Armada II (There is an option that appears under Graphics under Display Drivers when a secondary monitor is plugged in. While in battle, the secondary monitor shows a cinema shot of 5(+/-) seconds of any activity at any one place on the map. It continues to cycle through all the action on the map in 5(+/-) second intervals. Although, you have to have the cinema option enabled for it to work.)
  • Supreme Commander 2 has a multi-display for 2 monitors where the second monitor is a map of the battlefield
  • While not official, Minecraft has multiple monitor support because of its ability to drag the screen to any resolution the player wants.

See also[edit]


  1. ^ I. Berger(2006). The Virtues of a Second Screen. New York Times.
  2. ^ S.Ross (2003).Two Screens Are Better Than One. Microsoft research.
  3. ^ Z.Davis (2011). Dual Monitors Boost Productivity, User Satisfaction
  4. ^ Multi Monitor Computing by Nike Mikes and Dan Dunn, 9X Media, Inc.
  5. ^ Description of DualView in Windows XP
  6. ^ Dual monitors increase productivity. (2006-04-20). Retrieved on 2010-11-04.
  7. ^ "PCI Express - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. N.p., n.d. Web. 7 Feb. "PCI Express - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. N.p., n.d. Web. 7 Feb.
  8. ^ "Matrox Graphics - Products - Legacy Products - G-Series - G450." Welcome to Matrox. N.p., n.d. Web. 7 Feb. 2013. <>
  9. ^ Arar, Yardena. "When Two Monitors Aren't Enough | PCWorld." PCWorld - News, tips and reviews from the experts on PCs, Windows, and more. N.p., 8 Mar. 2012. Web. 7 Feb. 2013. <>.
  10. ^ Distributed multihead support with Linux and Xdmx
  11. ^ LambdaVision
  12. ^ "3D Surround Technology." World Leader in Visual Computing Technologies | NVIDIA. N.p., n.d. Web. 7 Feb. 2013. <>.
  13. ^ "AMD Eyefinity FAQs." Global Provider of Innovative Graphics, Processors and Media Solutions | AMD. AMD Graphics, n.d. Web. 7 Feb. 2013. <>
  14. ^ "AMD Eyefinity FAQs." Global Provider of Innovative Graphics, Processors and Media Solutions | AMD. AMD Graphics, n.d. Web. 7 Feb. 2013. <>
  15. ^ "3D Surround Technology." World Leader in Visual Computing Technologies | NVIDIA. N.p., n.d. Web. 7 Feb. 2013. <>.
  16. ^
  17. ^ Liquid Galaxy
  18. ^ ComroeStudios
  19. ^ Specifications of PCI-Express graphic card with 4 DisplayPort outputs.
  20. ^ "DisplayLink launches high-speed USB graphics technology for multi-monitor computing applications" (Press release). DisplayLink. April 11, 2006. Retrieved September 17, 2012. 
  21. ^ Bill Gates. April 7, 2006. How I Work. Fortune.
  22. ^ Hoetzlein, Rama C. Multi-Monitor Rendering in OpenGL
  23. ^ Dariusburst Another Chronicle Homepage
  24. ^ Dariusburst Another Chronicle Now Available Worldwide
  25. ^ Virtual Display Manager, Vista
  26. ^ MSDN Blog, Vista
  27. ^ NTI QuadStations- Fast, Multiple Screen Computers since 1995. Intel i7, nothing Faster. 2-12 Displays!. Retrieved on 2010-11-04.
  28. ^ "X-Plane 10 Desktop Manual : Configuring a Multi-Monitor Simulator,22 July 2013". Retrieved 29 December 2013. 
  29. ^ "How to run multiple copies of XP10 on one machine (Windows)". Retrieved 8 January 2014. 
  30. ^ "Howto: Take Advantage Of Multiple Graphics Cards/monitors In X-Plane - With A Single Computer! The Linux Way". Retrieved 8 January 2014. 
  31. ^ Supreme Commander Hardware Performance Guide, AU Game Spot, February 2007
  32. ^ Official DOOM FAQ, Section 9.2
  33. ^ Dual Display Gaming Bigs Up, Toms Hardware, February 2004
  34. ^ "Criterion Games Burnout Paradise The Ultimate Box on PC". Retrieved 29 July 2010. 
  35. ^ "Clear the Swarm FAQ". Retrieved 29 July 2010. 
  36. ^
  37. ^ MultiMonitor.Net
  38. ^ Essential Games List - WSGFWiki. (2010-01-19). Retrieved on 2010-11-04.

External links[edit]