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. Research studies show that, depending on the type of work, multi-head may increase the productivity by up to 50-70%.
- 1 Implementation of multi-monitor setups
- 2 Display modes
- 3 Products
- 4 Adoption of multi-monitor set-ups
- 5 Developing software for multiple monitor workstations
- 6 See also
- 7 References
Implementation of multi-monitor setups
Support for multi-monitor setup is either achieved by installing multiple graphics cards into one computer, or by special display controllers, that have the ability to feed multiple monitors independently with a signal. Monitors supporting DisplayPort allow to drive multiple monitors from only one external clock. DisplayPort version 1.2 supports Multi-Stream Transport, this makes it possible to drive multiple displays on one single DisplayPort connector using a multi-head cable or loop through.
The device driver usually includes the driver for the display controller, this software needs to support the hardware. Additionally the device driver should facilitate the configuration of the mode and of the display group. Additional software support may be required, examples are Xinerama and RandR.
Besides the single graphics card solution, there also solutions employing multiple graphics cards in one computer. And then there is the solution to connect multiple computers e.g. over Gigabit Ethernet/Ethernet to drive a large video wall. Software supporting the latter setup is Maxivista, ScreenRecycler, InputDirector, Synergy, or Xdmx.
The Electronic Visualization Laboratory at the University of Illinois at Chicago installed multi-monitor setup combining 55 LCD monitors which are connected to 32 PCs resulting in display resolution of 17600 × 6000 pixel.
The Institute of Visual Computing at the Bonn-Rhein-Sieg University of Applied Sciences set up a 7 x 5 display video wall resulting in 72 mega pixels resolution. 
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 presentations, 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).
Extended mode creates one huge virtual display with the added resolution of all participating monitors. Depending on the employed hardware and software, the monitors must be driven all with the same resolution or each monitor can participate with a different resolution.
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.
AMD Eyefinity has been available since September 2009 on various products. One graphics card can support up to six monitors. AMD Catalyst facilitates the configuration on all operating systems that it is available for, at least Microsoft Windows and Linux 32-bit and 64-bit.
Nvidia Surround has been available since June 2010 in the GeForce 200 series or newer. One 200, 400 or 500 series graphics card supports a maximum of two monitors. Nvidia: nView (Windows) / TwinView (FreeBSD, Linux), also multi-card.
Matrox graphics cards have long been the only products available, that support three monitors with one graphics card. Matrox additionally offers the Matrox Graphics eXpansion Modules product line including DualHead2Go and TripleHead2Go names. Software was called Matrox Powerdesk. The Matrox G450  can feature four outputs from one graphics card. In 3-monitor output setting, the 3rd monitor can only be used for video playback and cloning of 1 of the first 2 monitor outputs, but not an independent output. Also, when using Windows applications, for example, Internet Explorer, the 2nd output, will cut the edges of a maximized window 1 to a few pixels, making the scroll bar on the right thinner, the Close icon on the upper right smaller to be clicked, which was a bit clumsy.
The Intel product lines Intel GMA and Intel HD and Iris Graphics support multi-monitor set-ups with up to two monitors (dual display). The up-coming Skylake CPUs are going to drop support for VGA and support up to five monitors connected over HDMI, DP or eDP.
Adoption of multi-monitor set-ups
In the office
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.
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.
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, 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, it is not uncommon to see a wide range of business professionals using multiple monitors to increase visual area. 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.
Professional audio production
Digital audio workstation are known to rely on multi-monitor setups to increase the available area for the user interface.
In video gaming
Multi-monitor gaming/simulation is also becoming more common; however, the hardware expense can be a limiting factor.
List of video games that support multi-monitor set-ups
The following games support multiple screens inherently:
- Alien Isolation(PC)
- ArmA 3 (PC)(only works in span mode)
- Battlefield 3 (PC), FPS (only works in span mode)
- Battlefield 4 (PC), FPS (only works in span mode)
- Battlefield Hardline (PC), FPS (only works in span mode)
- BioShock (PC)
- BioShock 2 (PC)
- BioShock Infinite (PC)
- BioShock Infinite: Burial at Sea (PC)
- Borderlands 2 (PC),
- Burnout Paradise (PC), a racing game (only works in span mode)
- Clear the Swarm, a simple web game which utilizes dual screens, a primary for the main game and a secondary for additional information.
- Deus Ex: Human Revolution
- DiRT 2 (Eyefinity only)
- DOOM (early versions 1.0 and 1.1) permitted a three-monitor display mode, using three networked machines to show left, right, and center views.
- Eve Online
- Fallout 3 works in span mode using older NVidia drivers under Windows XP. It does not work under Extended Desktop in Windows 7, since extended desktop cannot define one large i.e. 2048x768 or similar spanned resolution.
- FlightGear (PC) An open source flight simulator that uses clear and simple XML files to configure multiple displays.
- Gran Turismo 6 since update 1.05
- IL-2 Sturmovik (WW2 flight simulator)
- iRacing.com supports triple monitors, and also supports individually rendering each display to reduce field-of-view distortion.
- Microsoft Flight Simulator 2000
- Microsoft Flight Simulator X
- R.U.S.E., a World War II Themed online Multiplayer RTS game.
- RailWorks (PC) supports double and triple monitor displays when not in full screen. When RailWorks is set to full screen, desktop spanning must be used if running Windows XP or AMD/ATI EyeFinity if running Windows 7.
- Ship Simulator 2008
- Supreme Commander and World in Conflict (DirectX 10 in multiplayer)[clarification needed] both support multiple monitors in a dynamic manner of effectively displaying two aspects of the game simultaneously.
- Test Drive Unlimited works in span mode using older NVidia drivers under Windows XP.
- Uplink (PC) featured a multi-monitor setup utilizing the screens of two networked computers. However, this option was removed in the 1.31 patch.
- X²: The Threat (PC) often cited as one of the first video games to utilize a multiple monitor setup
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. A larger list of games that support dual/multi screen modes is available at WSGF.
- 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.
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 games were released in the 1980s and 1990s which used a multi-monitor configuration. The earliest of these is the game TX-1, a 1983 driving game developed by Tatsumi and published by Namco/Atari, 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. The original 1987 arcade version of Tecmo Bowl also used a dual-monitor setup. In 1990, Galaxian 3 used up to 16 projected screens.
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 and worldwide the following year. It uses 2 32" LCD screens and an angled mirror to create a seamless widescreen effect.
Developing software for multiple monitor workstations
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.
|Wikimedia Commons has media related to Multi-monitor.|
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