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Multi-monitor, also known as Multi-display, Multi-head and Dual-Monitor are synonymous terms referring to 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. Microsoft describes this setup as "one of the best ways to improve your productivity".^[1][2] Randy Pausch recommended multiple monitors for improving personal productivity in his Time Management lecture.^[3]

Contents 1 History 2 Configuration and placement 2.1 Single PC multi-monitor 2.2 More than two monitors 2.3 Multiple PC multi-monitor 3 Display modes 3.1 Clone mode 3.2 Span mode 3.3 Hybrid Span mode 3.4 Extended mode 4 Commercial systems 5 Disadvantages 6 Tools 7 Graphics cards 8 Multi-display setups in the workplace 9 Other uses 9.1 Older uses 9.2 Other items of interest 10 See also 11 References

[edit] History

Contemporary versions of Microsoft Windows, Mac OS, and X Window System (used by GNU/Linux) all support multiple monitors. Dual monitor support once depended on specialized proprietary video drivers supplied with few video cards, along with a multi-display-supporting GUI system. Support for multiple monitor configurations was added as a standard feature in Microsoft Windows in Windows 98. It has been a standard feature in all versions of Apple's Mac OS X (introduced in March 2001), and was a standard feature of the first color Macintosh II introduced in 1987.^[4]

By adding up to two additional video cards, the Mac supported up to three monitors, although operating system support for multiple monitors wasn't introduced in Windows until the mid 1990s. The all-in-one Mac SE/30 featured a small black & white screen, but could drive an external color monitor.

[edit] Configuration and placement

In a multi-monitor configuration, an optimal layout is for each screen to be facing the viewer at the same distance.^[5]

[edit] Single PC multi-monitor

A multiple monitor setup increases the net display area of a system and can be an inexpensive way of improving computer usage.^[6] 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, 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 video card that supports two discrete outputs is referred to as Dual Head. Two separate video cards are just as acceptable, and so is using an integrated motherboard video socket plus a second video card, provided the integrated graphics are not automatically disabled by the installation of the peripheral card (a limitation that was common on older chipsets featuring integrated AGP graphics and an AGP upgrade slot).

[edit] More than two monitors

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. Given the bandwidth limitations of the older PCI bus, however, such setups were not common, and maximum overall graphics performance could only be obtained using specialty solutions such as the Matrox G450, 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. 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.^[7]

[edit] Multiple PC multi-monitor

Using 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,^[8] 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.^[9] This results in a 17600 x 6000 pixel display. As long as the xinerama extension is enabled, GNOME can use the entire desktop.

Software such as Maxivista for Windows and ScreenRecycler for Mac OS X let you set up multiple PC multi-monitor mode through virtual display drivers and client-side software.

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.

[edit] Display modes

[edit] Clone mode

Initially on PCs, the multiple output interface was designed to display the same image on all output interfaces (sometimes referred to as mirroring or cloning). This reflected the original use of these video cards in presentations where the user typically faced the audience and saw a duplicate of the projected image. Other modes have since become available.

[edit] Span mode

Alternatively, some video cards are able to "span" the existing desktop area across two monitors rather than create additional desktop space. This is accomplished by using a resolution such as 2048x768, with each monitor at a resolution of 1024x768. Both monitors need to have the same color depth settings, and often the same refresh rate. Differing resolutions may result in some screen space not being assigned to either monitor.

[edit] Hybrid Span mode

This is a technique that allows using multiple GPUs to create one single unified display. This is a driver feature which can overcome the 10 monitor limit in current Microsoft operating systems.

[edit] Extended mode

In "extended" mode, additional desktop area is created on additional monitors. Each monitor can use different settings (resolution, color, refresh rate). For example, a projector can show a presentation while the operator sees an advanced view of all slides. Macintosh computers have supported the "extended desktop" concept since the late 1980s, increasing the platform's utility for professional media and software developers such as graphic designers, video editors, and game developers.

The concept was further developed by PC manufacturers and led to the "extended" or "independent displays" mode and the "spanning" or "stretched" display mode. In both of these modes, display devices are positioned next to each other in order to create the illusion that the two displays are logically contiguous.

[edit] Commercial systems

Major players in the visual computing technologies currently include ATI Technologies (now a division of AMD), 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.

[edit] Disadvantages

The primary hardware disadvantage to dual 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 7MB 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 512MB 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. Furthermore, growth in 16:9 and 16:10 aspect ratio wide-screen LCD technologies has led to decreased cost for larger, wider displays, and some users may find that multi monitor does not add significant utility over a similarly-priced widescreen display.

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 RTS (RealTime Strategy) 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.

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 includes 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. Clicking in another display has a similar effect to hitting the Windows key or Alt-Tab, causing the desktop or another application to gain focus. The full-screen application loses focus, and may or may not pause any ongoing events in that application depending on how the software is written.

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 (ATI Tray Tools).

There are also some programs that provide full workarounds to the issue. One such utility is CSMMT^[10].

[edit] Tools

This section requires expansion.

The multi monitor tools available with the operating system, such as Microsoft Windows can be very limiting. Most of the drivers for video adapters capable of managing multiple monitors enhance the OS's features by their own. Aside from the VGA drivers few third party applications have been created to fill the gaps that the operating systems have not fulfilled. For Windows, Ultramon is a shareware utility that gives you much more control over multi monitor set-ups; Multimon is a free alternative. ATI provides the free Hydravision software for its cards. Yet another alternative is called SplitView. Such utilities enable users to perform functions such as:

• Give each monitor its own taskbar containing items open on that screen;
• Define keyboard shortcuts to perform such tasks as moving a window from one screen to the next, or rapidly moving the mouse pointer among monitors; and
• Set specific applications to open on specific monitors by default (e.g. set Microsoft Outlook to open on the secondary monitor by default).

For Microsoft Office, PowerShow is a shareware add-in that allows you to simultaneously display different Microsoft Office PowerPoint slide shows on different monitors in multi-monitor setups. PowerViewer is another shareware application that allows you to use the free Microsoft Office PowerPoint Viewer in multi-monitor setups for displaying different slide shows on different monitors. Multiple Windows for PowerPoint is yet another multiple monitor application for Microsoft Office PowerPoint that allows you to edit different presentations on different monitors.

For video playback over multiple monitors, some video player software will not span the video images across all these screens, due to hardware overlay limitation. It seems that there is one software called MatrixDvD Player can do this, it includes three playback modes: span mode, clone mode and select mode, the last mode can make you render the video content onto the monitors you select.

As with Windows, there are shortcoming to Mac OS X's multi-monitor support, just as there are solutions. The two biggest issues for a multi-monitor Mac user are; the inability to have the dock and / or the menu bar on both screens. This is useful as it allows faster access to the computer. The solutions to these problems are the use the freeware tool DejaMenu to allow a popup contextual menu containing all of the function of the OS X Menu Bar at the press of a key. To have more than one dock, the application DragThing will provide a dock substitute, it is shareware.

[edit] Graphics cards

The system display adapters will be provided with an array of outputs that will govern what is needed to complete a multi-monitor setup. Newer graphics cards are typically provided with two DVI ports supporting integrated VGA output, along with DVI-VGA adapters that will extract the VGA signal onto a conventional VGA port. CRT monitors will usually use VGA, but higher end CRTs may include DVI, and LCDs - depending on the model - can support either or both. Conventional or high-definition television outputs 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.

The most common setup for a pair of monitors is side by side, although graphics artists sometimes prefer to place one monitor above another.

[edit] Multi-display setups in the workplace

In many professions, including graphic design, architecture, 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.^[11]

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.

[edit] Other uses

[edit] Older uses

At one time, 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. 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 only supported grey-scale. 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.

[edit] Other items of interest

• The Nintendo DS, Dual Screen handheld system.
• The Wacom Cintiq is a drawing tablet/monitor combo, sometimes used alone, but it is often used as a secondary monitor.

Multi-monitor support

• OS
  • Microsoft (not official): Virtual Display Manager^[12]
  • X Window: Xinerama (deprecated) and XRandR 1.2
  • Nvidia: nView (Windows) / TwinView (Linux)
  • ATI: Hydravision
  • Citrix Presentation Server (Citrix ICA Client)
  • Microsoft Terminal Services (RDP Client) value: RemoteApp^[13]
  • Multi Display QuadStations -2-12 Displays ^[14]

Application support

• Adobe Photoshop Lightroom 2 can have images open on different displays and different viewing styles.
• Bloomberg Terminals use two or four monitors.
• Many programs in pre-ribbon Microsoft Office can have the toolbars moved to the second monitor.

Games support

• Clear the Swarm is the first web game officially supporting multiple monitors.
• Supreme Commander supports Multi-monitors in a dynamic way that effectively displaying two aspects of the game simultaneously.
• Uplink (PC) (which predates X²) features a multi-monitor option that utilizes the screens of two networked computers.
• Early versions of DOOM (1.0 and 1.1) permitted a three-monitor display mode, using three networked machines to show left, right, and center views.^[15]
• X2: The Threat (PC) often cited as one of the first video games to utilize a multiple monitor setup.^{[citation needed]}

[edit] See also

Wikimedia Commons has media related to: Multi monitor

• Multiseat
• UltraMon
• Two-Screen Solutions
• Xinerama

[edit] References