VideoChapter 17

OverviewIn this chapter, you will learn to

Explain how video displays work

Select the proper video card

Install and configure video software

Troubleshoot basic video problems

Video Video consists of two devicesthe video card (display adapter) and the monitor

The video card consists of two distinct componentsOne takes commands from the computer and updates its own onboard RAM

The other scans the RAM and sends data to the monitorMonitorVideo card

CRT Monitors

CRT All CRT monitors have a cathode ray tube (CRT), which is a vacuum tube

One end of this tube is a slender cylinder that consists of three electron guns

The wide end of the CRT is the display screen

CRT When power is applied to the electron guns, a stream of electrons is generated

This stream is subjected to a magnetic field generated by a ring of electromagnets called a yoke

The phosphor coating releases energy as visible light when struck by the electronsPhosphors continue to glow momentarily after being struckcalled persistence

CRT Refresh RatesCompTIA A+ EssentialsEssentials

CRT Refresh RatesHorizontal refresh rate (HRR)The speed at which the electron beam moves across the screen Vertical refresh rate (VRR)The amount of time taken by the monitor to draw the entire screen and get the electron beam back to the start

Video data is displayed on the monitor as the electron gun sweeps the display horizontally, energizing appropriate areas on the phosphor coating.

CRT Refresh RatesVideo cards push the monitor at a given VRR, and then the monitor determines the HRR

If the VRR is set too low, youll see flicker If it is set too high, youll have a distorted screen image and may damage the monitor

Multisync (multiple-frequency monitor) monitors support multiple VRRs

Phosphors Phosphors and shadow mask

Phosphors are dots inside the CRT monitor that glow red, green, or blue when an electron gun sweeps over them

Phosphors are evenly distributed across the front of the monitorOne group of red, green, and blue phosphors is called a triad

Shadow MaskShadow mask is a screen that enables the proper electron gun to light the proper phosphor

Electron guns sweep across the phosphors as a group

The area of phosphors lit at one time by a group of guns is called a picture element, or pixel

ResolutionMonitor resolution is always shown as the number of horizontal pixels times the number of vertical pixels

Some common resolutions are 640 x 480, 800 x 600, 1024 x 768, 1280 x 1024, and 1600 x 1200

These resolutions match a 4:3 ratio called the aspect ratio

Dot Pitch Dot pitchdiagonal distance between phosphorous dots of the same color

Range from 0.39 mm to as low as 0.18 mm

The lower the dot pitch, the more dots across the screen, which produces a sharper, more defined image

Bandwidth Bandwidthnumber of times an electron gun can be turned on or off per second

Bandwidth is measured in megahertz (MHz)VRR determined by bandwidth and resolutionBandwidth pixels per page = Maximum VRRFor example, a 17-inch monitor with a 100MHz bandwidth and a resolution of 1024 x 768 can support a maximum VRR of 127 Hz

100,000,000 (1024 x 768) = 127 Hz

LCD MonitorsLiquid crystal displays

Thinner and lighter

Much less power

Flicker free

Dont emit radiation

Called flat panels or flat panel displays

How LCDs Work Liquid crystals take advantage of the property of polarization

Liquid crystals are composed of specially formulated liquidLiquid is full of long, thin crystals that always orient themselves in the same direction

The crystals act exactly like a liquid polarized filter

Liquid Crystal MoleculesLCD monitors use liquid crystal molecules that tend to line up togetherThese molecules take advantage of polarizationFine grooves in a piece of glass will cause the molecules to line up along the grooves

Twisting MoleculesUse two pieces of glass with fine grooves oriented at a 90 angle

Molecules in the middle will try to line up to both sidescreating a nice twist

Add Polarizing FiltersNow add polarizing filters to both sidesThe liquid crystal will twist the light and enable it to pass throughAdding an electrical potential will cause the crystals to try to align to the electrical fieldTo darken an area, apply a charge

Passive MatrixUses three matrices to produce color

Above the intersections of the wires, glass covers tiny red, green, & blue dots

Slow and tends to create an overlap between pixels

Slightly blurred effect

Dual-Scan Passive MatrixRefreshes two lines at a time

Still used on some low-end LCD panels

Largely replaced with TFTThin film transistor

Thin Film Transistor (TFT) Thin film transistor (TFT) is also known as active matrix

It uses one or more tiny transistors to control each color dot

Brighter, with better contrast

Can handle a variety of colors, and has a much wider viewing area

Backlights illuminate the imageInverters power the backlights (with AC)

LCD logic board uses DC

Cold cathode fluorescent lamp (CCFL) used in backlightsLCD Components

LCD Resolution All LCD monitors have a native resolutionDisplay sharpest picture when set to this resolution

LCD panels cannot display more than their pixel limitation

When set to lower resolutions, image quality is severely degraded

LCD ComponentsBrightnessDetermined by backlightMeasured in nits (100 to 1000 with the avg. at 300)

Response rateSimilar concept as refresh rateLower rate (68 ns) betterLow-end LCDs (2025 ns) have ghosting problems

Contrast ratioDifference between lightest and darkestLow end (250:1) to high end (1000:1)

ProjectorsFront-view and rear-view

CRT projectors used first and are expensive

LCD projectors light and comparatively inexpensive

Today, almost all portable projectors are LCDs

Projector FeaturesLumensAmount of light provided by a light sourceHigher lumens = brighter picture

ThrowSize of an image at a certain distanceRelated to aspect ratio

LampsGet very hotExpensivetypically a few hundred dollars

Common FeaturesOverviewSizeConnectionsAdjustments

Common FeaturesSize CRT monitors measured in inches

Monitor size (not viewable area)

Viewable image size (VIS)screen size from diagonal corners

LCD monitors use just the VIS valueMonitor sizeVIS

Common FeaturesConnections Traditional CRT monitors use a 15-pin, 3-row, DB-type connector and a power plug

LCDs can use DB-15 or digital video interface (DVI)DVI-D (digital)DVI-A (analog)DVI A/D or DVI-I (interchangeable)DVI to VGA Adapter

Common FeaturesConnectionsThe Random Access Memory Digital-to-Analog Converter (RAMDAC) chip Converts digital signals into analog signals for analog CRTs

LCD monitors use digital signals Circuitry for converting analog signals to digital usually on board the LCD monitorsWhen using the DVI connection, not translated to analog (RAMDAC not used)Digital from video card sent and used as digital on LCD monitor

RAMDAC

Common FeaturesAdjustments ControlsOn/off buttonBrightness/contrast buttonOnboard menu system

Two main functions of menuPhysical screen adjustmentsColor adjustments

Power Conservation About half the power required by the PC is consumed by the CRT monitorMonitors that meet the VESA specs can reduce power consumption by +/75 percentDone with Display Power-Management Signaling (DPMS)

CRT monitor consumes +/120 wattsPower-down DPMS mode reduces to +/25 wattsFull shutoff DPMS mode reduces to +/15 wattsTakes about 1530 seconds to restore display

Power Conservation LCD monitor uses less than half the electricity as a CRT

19-inch 4:3 flat panel display uses +/ 33 watts at peak usageLess than 2 watts in DPMS modeReplacing CRTs with LCDs can have an impact on the electric bill

Video Cards

Video CardTwo major components

Video RAMStores the video image

Video processor circuitryTakes information from video RAM and sends it to the monitor

Video RAMText video cards display only the 256 ASCII characters Older systems displayed on 80 chars/row and only 24 rowsonly 1920 bytes of RAM needed

Graphics video cards could turn any pixel on or off Resolution of 320 x 200 pixels required 8 KBTo add color, multiple bits added 8 bits = 256 colors 24 bits = 16.7 million colors (true color)Color depth is represented as bits (color depth of 24 bits) and not the number of colors

Color DepthColor depth is represented as bits Color depth of 24 bitsNot the number of colors24 bits commonly referred to as true color

Number of ColorsNumber of Bits2 colors1 bit (mono)4 colors2 bits256 colors8 bits64,000 colors16 bits16.7 million colors24 bits16.7 million colors 8-bit opacity32 bits

Video ModesVGA (640 x 480)Beyond VGASVGA, XGA, and more

ModeResolutionModeResolutionQVGA320 x 240WSXGA1440 x 900WVGA800 x 480SXGA+1400 x 1050SVGA800 x 600WSXGA+1680 x 1050XGA1024 x 768UXGA1600 x 1200WXGA1200 x 800HDTV 10801920 x 1080HDTV 7201280 x 720WUXGA1920 x 1200SXGA1280 x 1024WQUXGA2560 x 1600

Motherboard ConnectionPCI slots800 x 600 with refresh of 70 Hz at 8 bits (256 colors) requires 33.6 Mbps bandwidth24 bits (16.7 million colors) requires 100.8 MbpsNot enough bandwidth available on shared PCI bus

AGP (accelerated graphics port)Dedicated to video Several advantages over PCI

AGP BenefitsAGP is a single special port dedicated to videoDerived from the 66-MHz, 32-bit PCI 2.1 specificationStrobing increases signals two, four, and eight times for each clock cycleUses its own dedicated data bus connected to NorthbridgeSupports pipelining Uses sidebanding (can send and receive at same time)Can steal chunks of regular system memory

PCIe (PCI Express)Developed to be replacement for PCIDesigned to replace AGP alsoIncredibly fast serial communicationsSupports many of the AGP benefitsSidebandingSystem memory accessPCIe card

The most important decision in buying a video card is the graphics processor

Most video processors are made byNVIDIAATI

ATI Radeon X1950 XTX 512 MBATIManufacturerRadeon X1950 XTXProcessor & Model No.512 MBAmount of RAM

Graphics Processor

Graphics ProcessorNVIDIA and ATI release multiple models of graphics processors each year

Most features only seen in 3-D gamesTexturesTransparencyShadowsReflectionBump mapping

Video Memory Video RAM constantly updates to reflect every change that takes place on screen

Three bottlenecksData throughput speedAccess speedSimple capacity

Overcome bottlenecks in three waysWider bus between video RAM and video processorSpecialized super-fast RAMMore RAM

Video Memory Bus widths64, 128, and even 256 bits wide

Most of the graphics rendering and processing is handled on the card Dedicated video processor rather than the CPU

Video MemoryVideo RAM Technologies

AcronymNamePurposeVRAMVideo RAMOriginalWRAMWindows RAMNever caught onSGRAMSynchronous Graphics RAMSpecial SDRAMDDR SDRAMDouble Data Rate SDRAMUsed on budget graphics cardsDDR2 SDRAMDDR Version 2Replaced with GDDR3GDDR3 SDRAMGraphics DDR V. 3Faster DDR2GDDR4 SDRAMGraphics DDR V. 4Upgrade of GDDR3

Installing and Configuring Video Software

Physical Installation IssuesTwo primary issues

Long cardsSome video cards are tall and may not fit in all casesGet a new case or new video card

Proximity to nearest PCI cardVideo cards run very hotLeave space for ventilationGood practice is to leave the slot next to an AGP card empty to allow better airflow

SoftwareTwo-step process

Load the driversInstall from CD or use built-in driver (if you must)Built-in driver likely the oldestCheck the manufacturers Web site for updates

Check the driversUse the Display applet

Display Applet Found in Control Panel or right-click the desktop and choose Properties

Making the screen prettyThemesDesktopAppearance

Other tabsScreen SaverSettings

Display AppletScreen Saver

Power Management features

Covered in Chapter 19

Display AppletSettings tabAllows you to configure multiple monitorsCan configure resolution and color depth

Display AppletAdvancedMonitor tab

Can update monitor driver

Can set the screen refresh rateChange in small incrementsCan cause damage

Display AppletAdvancedMany video cards have card-specific tab

Color CorrectionCan adjust screen colors

RotationPortrait or Landscape

ModesVery advanced settingsUsually not needed

Working with DriversVideo drivers work same way as other hardware driversCan access this screen from Device Manager or Device appletUpdate driverRoll back driverUninstall driver

As a basic ruleUninstall old drivers before installing drivers for new video card

IT TechnicianCompTIA A+ Technician3-D Graphics

3-D GraphicsImprovements driven by gamesAlthough improvements used in other applications such as computer aided design (CAD)

First-person shooters (FPSs) such as Wolfenstein 3D and Doom started move to 3-D

Transformation and SpritesMovement of 3-D objects referred to as transformation (CPU intensive)

Intels SIMD and AMDs 3DNow! expressly designed to perform transformation

Early 3-D games used sprites

Just a bitmap graphic moved around on the screen

Each figure had a limited number of sprites or angles of view

3-D ObjectsThe second generation produced 3-D objects thru a process called rendering

Composed of a group of points or verticesVertices were connected with lines (called edges)The edges form triangles that create polygonsThe last step is adding a texture (or skin)

3-D Video CardsGraphics processing units needed

Screens redrawn at least 24 times per second

3-D video cards have massive amounts of RAM for textures and fast processors for transformations

Application programming interfaces (APIs) created to talk to hardware directlyOpenGL ported from UNIXDirectX (Microsoft only)

DirectX and Video CardsDirectX provides direct access to hardware as follows:

DirectDraw: for 2-D graphicsDirect3D: for 3-D graphicsDirectInput: for joysticks and game controllersDirectSound: for waveformsDirectMusic: for MIDI devicesDirectPlay: for multiplayer gamesDirectShow: for video and presentation devices

DirectX Diagnostic ToolAccessories | System Tools | System InformationTools | DirectX Diagnostic ToolOrRun DXDiag

Web sitesSome useful Web sites to visit before making a hardware-buying decisionwww.arstechnica.comwww.hardocp.comwww.tomshardware.comwww.sharkyextreme.com

Troubleshooting Video

Video Card Problems Vast majority of problems areImproper or corrupt driversIncorrect settings

Incompatible or corrupt driver symptoms640 x 480 mode16-color VGA

Your responseBoot into safe mode and remove driverUse Add/Remove programs if availableUse Device Manager

Video Card HW ProblemsHardware problems usually just one of two Fan has gone outRAM is faulty

Faulty hardware symptomsBizarre outputMay see mouse movingDisplay is a mess

Video Card ProblemsDont forget the obviousIf everything is sideways, check the rotation settings

Limited colorscheck the color depth

Resolution set too highInput signal out of range

Troubleshooting MonitorsOpening up a monitor can be deadly

Even when the power is disconnected, certain components inside a monitor retain a substantial voltage for an extended period of time. If you accidentally short one of the components, it could actually kill you!

Troubleshooting MonitorsDangerous inside a monitor

Proper adjustment requires specialized training

Your goal is to determine if a problem is in one these three categories:Common monitor problemsExternal adjustmentsInternal adjustments

Common Monitor ProblemsControl buttons are replaceable Check with the manufacturer

Ghosting, streaking, fuzzy vertical edges Check the cable connections and cable itself

Missing color Check cable for breaks, bent pins, and monitor adjustments

Loss of brightness Normal with age, so use power managementInternal adjustments may be made

Common ProblemsCRTsYou may be able to fix thisBig color blotchesdegauss it with degauss button

Its probably beyond fixingDim display (with brightness turned up)

Take it in to a repair shopOut of focusadjustment near the flyback transformerHissing or sparking sounds Bird-like chirping soundsSingle horizontal or vertical lineSingle white dot on a black screen

Troubleshooting Monitors External controls provide users with the opportunity to fine-tune the monitors image

Brightness and contrast

Pincushioning

Trapezoidal adjustments

Tint and saturation of color

Monitors have a built-in circuit called a degaussing coilEliminates magnetic build-up A fuzzy looking monitor may be fixed by degaussing itDisregard the loud thunk soundits normal

Troubleshooting CRTsConvergence defines how closely the three colors will combine

Misconvergence causes halosMost likely near the edges of the screenCan be set by internal adjustments

Schematics of monitor will show location of variable resistor that can be adjustedManufacturers wont give you the schematicsLeave to a trained specialist

High-Voltage AnodeUnder the suction cup is the actual high-voltage anode

The wire leading from the suction cup goes to the flyback transformer

Theres a big capacitor that can hold up to 25,000 volts of charge for days, weeks, months, or even yearsLifting this suction cup will almost certainly kill you!High-voltage anode

Do NOT attempt todischarge a monitorunless properly trainedand equippedDischarging a CRT

Common ProblemsLCDsSymptomsCracked LCD monitors: not repairableLCD goes dark: lost either lamp or inverterHissing noise: inverter is about to fail

LCD repair companiesSpecialize in repairing LCD monitors

Bad pixelsNormal to have some bad pixelsDead pixel: never lights upLit pixel: stays on pure whiteStuck pixel: stays on certain color

Cleaning Monitors Anti-static monitor wipes or anti-static cloths should be used for cleaning the monitor

Do not use window cleaners

Avoid commercial cleaning solutions on LCD screens

Beyond A+Video setting for EGA/VGA Has no meaning today and is ignored

Init Display FirstDetermines which monitor to boot first in a multi-monitor system

Assign IRQ for VGANot needed for low-end cardsHigh end: Try it each way

VGA Palette SnoopNot used today

Video Shadowing EnabledTypically ignored but sometimes required to be off

SLI and CrossfireSplitting the processing load between two or more GPUsNVIDIA calls theirs Scalable Link Interface (SLI)ATI calls theirs CrossFire

Two video cards installed and connected with a bridge card

TV and PCsTV Out connects computer to TV

Tuner cardsAllows PC to mimic some features of Tivo

HDMI (High Definition Multimedia Interface)Designed to replace DVI connections

PlasmaNot suited for PCsOdd native resolutions (such as 1366x768)Burn-intendency for a screen to ghost an image

DLPDigital light processing

SED, FEDCombines CRT strengths with LCD strengthsSurface-conduction electron emitter displayField emission display

TV and PCs

****Before we begin, a note of warning about the inside of a traditional monitor. I will discuss what can be repaired and what requires more specialized expertise. Make no mistakethe interior of a monitor might appear similar to the interior of a PC because of the printed circuit boards and related components, but that is where the similarity ends. No PC has voltages exceeding 15,000 to 30,000V, but most monitors do. So lets get one thing perfectly clear: Opening up a monitor can kill you! Even when the power is disconnected, certain components retain a substantial voltage for an extended period of time. You can inadvertently short one of the components and fry yourselfto death. Given this risk, certain aspects of monitor repair lie outside the necessary skill set for a normal PC support person and definitely outside the A+ Certification test domains! I will show you how to address the problems you can fix safely and make sure you understand those you need to hand over to a monitor shop.

*Tech TipPerfect flatLots of manufacturers make CRT monitors, but only a handful of companies make the CRTthe tube inside the monitoritself. All CRT tubes can be categorized into either of two types: traditional curved-screen CRTs and CRTs that are often referred to as perfect flatusing a new kind of vacuum tube that has a completely flat screen and no bending around the edges. The perfect flat screens offer a wider viewing angle than standard CRT screens. About the only negative to perfect flat screens is that they tend to lack true black, so pictures seem just shy of a natural richness of color and contrast. ****When most techs say refresh rate, they really mean the VRR.

*Tech TipTrinitronNot all monitors use dots. The popular Sony Trinitron line of CRT monitors uses bars of red, green, and blue instead of dots. The holes in the shadow mask have a rectangular shape. Many people feel this makes the monitors image much crisper and clearer. Somebody must agree with them since the Trinitron enjoys tremendous popularity. Even though the phosphors and shadow mask have a different shape, everything you learn here applies to Trinitrons also.

***When comparing advertised prices, make a note of the monitors dot pitch in the ad. Watch out for lower priced monitors with an unacceptably high 0.39-mm dot pitch. By comparison, a mid-priced television has a dot pitch of approximately 0.35 mm. Also beware of monitor advertisements citing the horizontal dot pitch, which is a smaller number (often around 0.22 mm) instead of the standard vertical dot pitch. ***Light comes to us in many different wavelengths. Seeing many different wavelengths at one time causes us to perceive white light.If light came to us in just one wavelength, we would only see one color.When light travels thru a polarizing filter (such as a pair of sunglasses), all wavelengths get throughjust fewer of them, so things appear darker.If you put two polarizing filters at a 90-degree angle, no light would get through. Put at various other angles and some light gets through.

********Tech TipDealing with high-resolution LCDsThe hard-wired nature of LCD resolution creates a problem for techs and consumers when dealing with bigger, better quality monitors. A typical 15-inch LCD has a 1024 768 resolution, but a 17-inch usually has 1280 1024 or higher. These high resolutions make the menus and fonts on a monitor super tiny, a problem for people with less-than-stellar vision. Many folks throw in the towel and run these high-end LCDs at lower resolution and just live with the lower quality picture, but thats not the best way to resolve this problem. With Windows XP (and to a lesser extent with the earlier versions of Windows), Microsoft allows incredible customizing of the interface. You can change the font size, shape, and color. You can resize the icons, toolbars, and more. You can even change the number of dots per inch (DPI) for the full screen, making everything bigger or smaller!For basic customizing, start at the Control Panel, Display applet, Appearance tab. To change the DPI for the display, go to the Settings tab and click the Advanced button. Your clients will thank you! *****Not many people use the term LCD monitor. Instead, youll often hear the terms flat-panel display or LCD panels. I prefer the term LCD monitor, but be prepared to hear it a few different ways.

*****Tech TipsPower switch vs. DPMSTurning off the monitor with the power switch is the most basic form of power management. The downside to this is the wear and tear on the CRT. The CRT is the most expensive component of a monitor, and one of the most damaging things to a CRT is to turn it on and off frequently. When using a non-DPMS monitor or video card, it is best to turn the monitor on once during the day, and then turn it off only when you are finished for the day. This on-off cycle must be balanced against the life of the CRT display phosphors. The typical monitor will lose about half its original brightness after roughly 10,000 to 15,000 hours of display time. Leaving the monitor on all the time will bring a noticeable decrease in brightness in just over a year (8766 hours). The only way around this is enabling the DPMS features of the monitor or taking care to turn the monitor off.

Using DPMS to your advantageHave you ever looked closely at the screen on an ATM? If so, youve likely seen the burn-in effects that occur when a monitor is left running 24/7. You should be able to see the Welcome to XXXXX Bank, please insert your card message faintly. If ATMs used DPMS, this could be avoided. Of course, this is a worst-case scenario and it would take a long time for this type of damage to happen to your PC monitor. However, its always a good idea to use the DPMS settings and have your monitor turn off after a designated period of inactivity. Personally, I set my monitor to shut off after 30 minutes of non-usethat period of time is long enough to allow me to get up, make a sandwich, and return to my computer without my monitor taking a nap but short enough to prevent any damage from occurring. *****Know your color depths both in terms of bits and numbers of colors!

*******Gaming requires high-end video cards for the best effects:

3-D textures are bitmap graphics applied to 3-D wireframes like skin over bones. Applying a pre-made texture to a wireframe drawing is called rendering.Textures are not large but games may require hundreds.To store these more RAM is needed. Advanced 3-D video cards may have up to 128 MB of RAM.Video display memory ranges from 32 bits to 256 bits wide.******Especially useful for LCD monitor users, including folks with portable computers, is the Effects button on the Appearance tab of the Display Properties dialog box. The second option gives you a choice of font smoothing techniques, and many users exclaim joyously when they change the default from Standard to Clear Type. ******************Safety AlertBefore we go any further here, lets discuss a serious safety issue. Unless you are specifically trained in TV repair or other high-voltage work, under no circumstances should any student or technician open up a monitor case. It is way beyond the scope of CompTIA A+ Certification, and it is way beyond the scope of an A+ Computer Service Technicians training and abilities. Monitors have very high voltage inside that can kill! Monitors can hold this charge in their capacitors even after being unplugged for days, weeks, months, even years! If you accidentally touch the wrong thing inside a monitor, you might wind up dead!**Tech TipThe only time Ill open a monitor is to replace a control knob or switch or to try and adjust the focus. These tips are great to know for the CompTIA A+ Certification exams, but Im just way too chicken to do most of these myself. Here is a list of a few last dos and donts that I abide by to keep my monitors happy: Do keep the screen clean. Do keep the cables tightened. Do use quality cabling. Do use power-management features if available. Dont block the ventilation slots on the monitor. Dont use a refresh rate higher than recommended by the manufacturer. Dont leave the monitor on all the time, even with a screen saver. Dont place magnetic objects such as unshielded speakers close to the monitor. (This can cause color problems at best and could permanently magnetize the shadow mask at worst.) Be careful when disposing of a dead monitor. Many local governments have laws regarding safe disposal of monitors. Be sure to check with your local waste disposal entity, or your company, to verify proper disposal methods.

****Discussion TopicMonitor repairBecause as a A+ Computer Service Technician you should not attempt to open or repair monitors, you may be able to align your business with a local TV repair shop. If you are not able to strike a deal with a local shop, either have the customer take the failing monitor to a TV repair shop of their choice or suggest they replace it. In many cases, the cost of a repair will surpass the cost of a new monitor.****ExerciseTroubleshootingSurreptitiously change settings in the CMOS, control panels, and monitor settings. On some, just do the simple trick of turning down the brightness on the monitor. Delete the video driver, and, after rebooting, have the students try to adjust the number of colors or resolution. Delete the monitor driver, and, after rebooting, have them try to change the refresh rate.****