Multisync monitor: Difference between revisions

Revision as of 02:44, 13 December 2014

Revision as of 09:43, 16 January 2015

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A '''multisync monitor''' or '''multiscan monitor''' is a [[Computer display|monitor]] that can properly [[Synchronization|synchronise]] with various [[Horizontal scan rate|horizontal]] and [[Vertical synchronization|vertical]] scan [[Frequency|frequencies]].<ref>{{cite web|title=13 What's the difference between fixed frequency and multisynchronous monitors?|url=http://stason.org/TULARC/pc/video-faq/13-What-s-the-difference-between-fixed-frequency-andmultisynchronous-monitors.html}} 070808 stason.org</ref> In contrast, fixed frequency monitors can only synchronise with a specific horizontal and vertical frequency, limiting their flexibility.

Multiscan monitors appeared during the late 1980s ,<ref>{{cite web|title=MultiSync 25th Anniversary - The Evolution of the MultiSync|url=http://www.nec-display.com/ap/en_display/25th/}}</ref>, offering flexibility as computers moved from earlier standards such as [[PAL]], [[NTSC]] and [[Color Graphics Adapter|CGA]] to higher scan-rate standards such as [[Enhanced Graphics Adapter|EGA]], [[VGA]] and [[SVGA]]. Normally, a different fixed-frequency monitor was required for each of these standards. <!-- the wiki articles on VGA etc. should already cite all needed information -->

# [[PAL]], [[NTSC]], [[Color Graphics Adapter|CGA]]: ~15&nbsp;kHz horizontal scan, 50-6050–60&nbsp;Hz vertical scan

# [[Enhanced Graphics Adapter|EGA]]: ~23&nbsp;kHz horizontal scan

# [[VGA]]: ~31&nbsp;kHz horizontal scan, 60-7060–70&nbsp;Hz vertical scan

# [[SVGA]]: 31&nbsp;kHz - 100&nbsp;kHz+ horizontal scan, 50&nbsp;Hz - 120&nbsp;Hz+ vertical scan

By the late 90s, multiscan monitors had become standard for personal computers, supporting a range of resolutions and refresh rates. A typical screen resolution of the time was 1024x768 at 85Hz85&nbsp;Hz <!-- need to find archived personal computer manufacturer product listings and web browser statistics for citation -->, requiring a horizontal scan rate over 85kHz85&nbsp;kHz,<ref>{{cite web|title=Modeline Calculator|url=http://www.arachnoid.com/modelines/}}</ref> yet during system boot the [[Power-on self-test|POST]] display and [[operating system]] splash screen would be displayed at the standard VGA 31kHz31&nbsp;kHz. Many [[MS-DOS]] and [[Windows]] computer games of the time would also switch to a lower resolution for greater compatibility, more colours, improved performance or to reduce the [[video memory]] required by the [[frame buffer]].

Depending on the design of the monitor, there may be several discrete frequencies supported. For example, a monitor designed for use with CGA, EGA and VGA standards could elect to support 15kHz15&nbsp;kHz, 23kHz23&nbsp;kHz and 31kHz31&nbsp;kHz horizontal scan rates. Alternatively, the monitor may be designed to support a continuous range from 15kHz15&nbsp;kHz to 31kHz31&nbsp;kHz. <!-- links to product manuals for old multisyncs would be useful here, or usenet -->

A multiscan monitor does not need to support all possible video formats. Most modern multiscan computer monitors support a nearly-continuous range of horizontal scan frequencies from 31kHz31&nbsp;kHz up to 100kHz100&nbsp;kHz+, omitting support for the older 15kHz15&nbsp;kHz - 23kHz23&nbsp;kHz standards. <ref>{{cite web|title=comp.sys.amiga.misc usenet post circa 1992|url=https://groups.google.com/forum/#!search/Multisync/comp.sys.amiga.misc/ktCKO1yqiaY/WB2ky14SDEYJ}}</ref> <ref>{{cite web|title=comp.sys.acorn.hardware usenet post circa 2010|url=https://groups.google.com/forum/#!search/Multisync/comp.sys.acorn.hardware/ZFi8regDZeo/gEGWCHGWLm8J}}</ref>

Fixed-frequency [[Cathode ray tube|CRT]] monitors, and multiscan CRT monitors that only support a set of frequencies, may upon receiving scan frequencies outside design limits cause damage to the monitor. This is especially true for horizontal scanrate, which in CRT monitors is associated with higher voltages and power levels. A resonant circuit is commonly employed, restricting the allowable horizontal scan rates to one or more very narrow ranges. Not all fixed-frequency monitors are vulnerable to damage, but it is never safe to assume this. Most modern multiscan monitors are [[microprocessor]] controlled and will refuse to attempt to synchronise to an unsupported scan rate, which usually protects them from damage.

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The terms "multisync" or "multiscan" do not apply to [[LCD]] monitors in the same way they do to [[Cathode ray tube|CRT]] monitors. LCD monitors are [[fixed-pixel monitors]]. For compatibility with boot screens and legacy software, stand-alone LCD monitors are usually required to support VGA scan rates in addition to their native resolution. In order to support the lower resolutions, a circuit is used to convert the incoming signal to the monitor's native resolution. The resulting image either appears in a small 1:1 pixel mapped window, or more commonly is stretched to fill the screen. In the latter case, the circuitry is referred to as a [[Video scaler|scaler]]. <!-- scaler article has all the citations -->

While stand-alone LCD monitors generally accept a wide range of horizontal scan rates, the same is not true of the vertical scan rate. The vast majority of LCDs accept only 60Hz60&nbsp;Hz to 70Hz70&nbsp;Hz vertical scan rates. In recent years, LCD monitors designed for gaming have appeared on the market offering vertical scan rates of 120Hz120&nbsp;Hz and up. <ref>{{cite web|title=List of 120Hz monitors - Includes 144Hz, 240Hz Blur Busters|url=http://www.blurbusters.com/faq/120hz-monitors/}}</ref> These monitors are referred to by the term "120Hz" (or the applicable refresh rate) rather than "multiscan."

MultiSync is a trademark of [[NEC]].

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[[Category:Display devices]]

[[Category:Graphics hardware]]

{{Compu-graphics-stub}}