Multi-monitor

File:Dual apple monitors.jpg

Dual displays allow for increased desktop space, as well as a wider area of vision.

Multi-monitor, also known as 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".

Configuration and placement

When configuring the layout of your Multiple-Monitor system it is imperative that you use a layout which will provide optimum productivity. According to This Article:

The optimal layout is for each screen to be equidistant from the viewer, pointed directly at the viewer [...] A 180-degree encapsulation is the best. Then again, I don't mind turning my head sometimes as long as the main concentration of information (Specifically, actively productive information) is within the front-center 30-degree arc.

By the Pythagorean theorem, the corner-to-corner distance of an 8 1/2"-by-11" piece of paper is about 13.9", not much smaller than the display sizes seen in many offices. In the article Two Screens Are Better Than One, Gary Starkweather, inventor of the laser printer, asks, "What if I took away your desk, and gave you one that was only 8-by-11? How easy would it be for you to work?" His point is that a larger desk space is less awkward to work with, whether the desk is physical or virtual.

Single PC multi-monitor

Setting up multiple monitors can be an inexpensive way of improving computer usage.[1] It increases the display area, although it is still limited by the size, resolution and number of the 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 card and is interpreted and displayed by a variety of devices. Video cards are typically 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 has two sockets on it (for two monitor cables) is referred to as Dual Head. Two separate video cards are just as acceptable, and so is using the motherboard video socket plus a second video card.

More than two monitors

Since computers with two or more PCIe interfaces are getting more popular, high-end computer users no longer feel limited to two monitors driven by a single main graphics adapter. It is not too uncommon to see users with three or even four monitors connected to a system with multiple graphics adapters. If a dual PCIe interface is not available, a standard PCI graphics card can be used along with a PCIe or AGP card to extend to two or more monitors. Also, some specialized cards support more than two monitors with a single card. Particularly in CAD, Day-Trading, and Software Development environments, it is gradually becoming more common to see as many as six or more monitors on one production system [2].

A Quad Monitor Audio Workstation

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, 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. 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. ScreenRecycler uses VNC to achieve this by setting up the primary PC as a VNC server, and configuring other PCs as VNC clients that display the primary PC's extended desktop. Each of these can also be set up to allow desktop sharing.

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.

Synergy is an open source alternative that can be run on almost any operating system (Windows, Linux/Unix and Mac.) It has no limit to the number of computers/monitors that can be set up in such a way, though it does not configure multiple monitors connected to a single computer.

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.

History

Contemporary versions of Microsoft Windows, Mac OS, and X Window System 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 (Mac II) introduced in 1987.

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.

Display modes

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 fact that these video cards were originally used in presentations where the user typically had his or her face to the audience with a duplicate of the projected image available to the presenter.

Span mode

Alternately, 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 each monitor at 1024x768 resolution. Each monitor needs to have the same resolution and color depth settings, and often the same refresh rate.

Extended mode

In "extended" mode, additional desktop area is created on additional monitors. Each monitor can use different settings (resolution, color, refresh rate). Macintosh computers have supported the "extended desktop" concept since the late 1980s, providing a robust experience for graphic designers, video editors, and even game developers.

This 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 these modes, display devices are positioned next to each other in order to create the illusion that the two displays are logically contiguous.

Commercial systems

Three main commercial video card competitors are ATI Technologies with its Hydravision, Matrox with its DualHead Multi-Display and NVIDIA's nView. The technology was once limited to the professional graphics market, but with the advent of more powerful graphic processing units, and the bundling of the software with the respective display cards, penetration into the consumer market has been enabled. The latest versions of MS Windows support up to 64 monitors. The largest Multi-Monitor Computer manufacturers are SUPER PC and DigtelTigers.

Disadvantages

The primary disadvantage to the usage of dual monitors is that the resources of the video card are effectively halved when the second display device is connected. The decreased processing power and VRAM available to each display may lead to unacceptable performance on both devices. In this case, the second display device may be connected to an additional video adapter installed in the computer allowing the full processing and VRAM capability for each device. However, as newer and more powerful graphics cards are introduced, this problem is not so much of an issue.

Full-screen software also poses a problem on multi-monitor PCs. A large amount of full-screen applications makes use of the absolute edge of the display to control view movement. Unfortunately, this software generally does not work properly on a multi-monitor PC unless the software specifically was designed to be multi-monitor aware.

You can often find “edge-scrolling” in full-screen image viewers, 3D model editors, and RTS (RealTime Strategy) genre video games.

Despite that the use of multi-monitor PCs is steadily growing, there still are significantly more single monitor PC users out there. As a result of this vast majority of single display users, software developers often see adding multi-display support to their titles as a low priority (since so little of their potential market-base uses multi-display systems). This will likely change someday as the percent of multi-monitor PC users increases, yet at present multi monitor computing is still fairly limited in the home consumer market.

The problem that full-screen applications present is that they generally only cover one of the displays on a multi-monitor computer. Edge-scrolling still works in these applications if you position the mouse cursor on the absolute edge of the screen, yet this is often impractical and hard to do. The reason that you cannot easily position the mouse on the absolute edge is simple; the desktop space on a multi-monitor PC is not limited to just that display. Instead of the mouse cursor stopping at the screen's edge (where the software developers assumed that it would), the cursor migrates into the adjacent monitor's desktop space.

It turns out that this is actually much more of a problem than one might first think. All sorts of severe problems can 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. In other words, clicking on another display causes the desktop to gain focus, which in turn causes the full-screen application to lose focus.

Ideally, software should be written to be multi-monitor aware. However, until that happens there is a variety of ways to overcome the edge-scrolling problem.

One of the most common methods of overcoming the edge-scrolling problem is to set up your multi-monitor orientation on a diagonal. With a diagonal orientation there is no desktop space to the left, right, top, or bottom of the full-screen application. What this does for full-screen applications is prevent the mouse cursor from moving beyond the screen edge (since there's no desktop space there), thus permitting the user to edge-scroll properly. As a downside, a diagonal orientation can make moving the mouse from monitor to monitor difficult. It also often does not match the physical arrangement of monitors, adding to difficulty in working between displays.

Another method is to temporarily remove the offending monitors (literally). While this clearly lets a person run their software properly, it may not be desired to disable all other displays. On a Windows platform removing displays from the screen layout tends to also push all 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.

Tools

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The corner of a window; the two leftmost icons, added by Ultramon, move the window to the next screen or spread it across two screens.

File:Multimon.gif

Multimon adds icons allowing the window to be shifted to the monitor that is either left or right of the current one.

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 enables 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).

Graphics cards

The interface of the system's graphics cards governs what is needed for the setup. Newer graphics cards usually come with 2 DVI ports (with DVI-VGA adapters available to connect to monitors that use VGA). CRT monitors will usually utilise VGA, but higher end CRTs can use DVI and LCDs depending on the model can support either.

The most common setup for a pair of monitors is side by side (as pictured above) however it isn't uncommon for those who work with graphics to place (sometimes for short periods of time) a monitor above another.

Multi-display setups in the workplace

An Office Worker with Dual Monitors

In many professions, including graphic design, architecture, engineering and video editing, the use 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.

Now that Multi-Monitor setups are more budget-friendly, it is not uncommon to see other professionals use multiple monitors to quickly view documents, webpages and webpages side-by-side. This advantage helps push the idea of a paperless office, and is helping to make it more feasible. However, the use of a large widescreen monitor also permits viewing of two documents side-by-side, however this approach has the disadvantage that windows will not maximize to half the screen size.

Other uses

Older uses

It was, for a time, a popular configuration for software developers to have a VGA or EGA display for the program under development and an independent monochrome Hercules or MDA card driving a separate monitor for debugging. Many DOS debuggers supported this configuation. It was possible to operate two display cards, even with operating system which does not support multi-monitor (like MS-DOS), because Hercules and MDA use different memory address than any other cards (CGA/EGA/SVGA...). 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 colour even though the main monitor only supported grey-scale.

Other items of interest

• The Nintendo DS handheld system has two color LCDs placed vertically.
• The Wacom Cintiq [3] is a drawing tablet/monitor combo, sometimes used alone, but it is often used as a secondary monitor.
• The PC game Supreme Commander supports Multi-monitors in a dynamic way, effectively displaying two aspects of the game simultaneously.
• The PC game X²: The Threat often cited as one of the first video games to utilize a multiple monitor setup.
• The PC game Uplink (which predates X²) features a multi-monitor option that utilises the screens of two networked computers.
• Bloomberg Terminals use two monitors.
• Multi-monitor support within remote sessions such as Microsoft Terminal Services (Microsoft RDP client) or Citrix Presentation Server (Citrix ICA Client) - one of the existing solutions is a Virtual Display Manager [4]

See also

• Multiseat
• Multi Screen Computer