Presentation on theme: "Supporting I/O Devices"— Presentation transcript:
1 Supporting I/O Devices Monitors & Video CardsSupporting I/O Devices
2 PC Displays Primary output device of a computer is the monitor Monitor, Video Display, VDT, Screen…..Two necessary components for video outputVideo controllerMonitor
3 PC Displays CRT- Cathode Ray Tube A CRT monitor uses a vacuum tube to contain the beam of electrons used to produce the imageTwo Types:RegularFlat-technology monitors
4 PC Displays Flat Panel Technology LCD : Liquid Crystal Display Flat panel monitors are built to receive either an analog signal or a digital signal from the video card and have two ports on the monitor to accommodate either signalFlat Panel TechnologyLCD : Liquid Crystal DisplayPDP: Plasma Display PanelA gas plasma displayELD: Electroluminescent displayLED: Light Emitting Diode
5 Display Subsystem Each PC’s display subsystem consists of three parts: Video Display Adaptercreates and holds the image informationMonitordisplays the informationCableconnects the video adapter to the monitor
6 Display BasicsPixelsIn a CRT display device, the smallest possible pixel is actually a dot trio called a triada red, green and blue phosphor dot setRGB Model - most common model for PC video displays
7 Display BasicsAn electronic beam is used to strike the phosphor causing it to emit lightPlates on the top, bottom and sides of the CRT tube control the direction of the beamDepending on the intensity of the beam, the dot trio emits a range of colors created by mixing the 3 colors: red, blue and green
8 Computer Display Systems CRT- Cathode Ray tube- the same technology employed by your television- an electron gun scans the screen causing special chemicals called ‘phosphors’ to glow- the gun scans from top to bottom, left to rightVideo Adapter- an expansion board or integrated device that renders characters for display in response to commands from the computer- it tells the display device how to draw the graphic
9 Video TechnologiesMonochrome- two color video- text only with a resolution of 720 x 350Color Graphics Adapter- CGA- four colors- 320 x 200 resolution for graphics, 640 x 200 for two colorEnhanced Graphics Adapter- EGA- 16 colors- 320 x 200 graphics, 640 x 350 textVideo Graphics Array- VGA- introduced with the IBM AT form factor motherboards- used an analog signal- 256KB of video memory on board- 16 colors at 640 x 480 or 256 colors at 320 x 200Super Video Graphics Array- introduced by the Video Electronics Standards Association- 65, 536 colors at 640 x 480, 256 colors at 800 x 600 or 16 colors at 1,024 x 768Extended Graphics Array- IBM’s answer to the SVGA, XGA could only use the MCA expansion bus- it also used interlacing, or scanning every other line on each pass- offered the same resolution options as the SVGA
10 Display Quality Measurements Dot Pitch- the shortest distance between two dots of the same color on the monitorMeasured in millimetersThe lower the number, the sharper the image.28mm is considered average- anything smaller is greatRefresh Rate- vertical scan frequency- how many times in one second does the electron beam redraw the screen? The standard is 60Hz for VGA
11 DisplaysMost desktop displays use a cathode ray tube (CRT), while portable computing devices such as laptops incorporate liquid crystal display (LCD)Because of their slimmer design and smaller energy consumption, monitors using LCD technologies are beginning to replace the venerable CRT on many desktops
13 DAC Converters Digital-to-Analog (DAC) Converters special integrated circuits used by display adapters
14 Two Ways to Paint Image on Screen: Vector Displaysthe electronic beam used to create the image is moved across the screen in a pattern similar to moving a pen or pencil over a piece of paper
15 Two Ways to Paint Image on Screen: Raster-Scanthe screen is painted line by line from left to rightthe electronic beam is played across the screen from left to right in a straight horizontal line - moves to left and goes to next lineMost CRTs and LCDs use Raster-Scan to paint images to screen
16 Liquid Crystal Displays Active Matrix- each LCD pixel has a transistor behind it to activate or deactivate the crystalVery crisp and easy on the eyesVery power intensive- severely limited the amount of time a laptop could run on battery powerPassive Matrix- two rows of transistors marking the x and y coordinates of a grid- a signal voltage line is sent to the x and y coordinates, turning the corresponding pixel darkRequires less powerSacrifices image qualityResponse of the screen to rapid change is poorWhen Passing an electrical current through a semicrystalline liquid, the crystals would align themselves with the currentSubmarining - an image, rather then moving, will disappear from spot and reappear in another
17 LCD panelsAn LCD is made with either a passive matrix or an active matrix display display gridThe passive matrix LCD, which is older technology, has a grid of conductors with pixels located at each intersection in the grid.The active matrix LCD is also known as a thin film transistor (TFT) display, which has a transistor located at each pixel intersection, requiring less current to control the luminance of a pixel.
18 LCD panelsA color LCD must have three subpixels with red, green and blue color filters to create each color pixelThrough the careful control and variation of the voltage applied, the intensity of each subpixel can range over 256 shadesCombining the subpixels produces a possible palette of 16.8 million colors
19 LCD technologyLCDs today employ several variations of liquid crystal technology, e.g. ferroelectric liquid crystal (FLC)Display size is limited by the quality-control problems faced by manufacturersThe more transistors that are put in display, the chances are that the will be defectiveManufacturers of existing large LCDs often reject about 40 percent of the panels that come off the assembly line
20 LCD MonitorsIn general, an LCD panel is made of two polarized planes of glass placed at right angles (90 degrees) to each other.Sandwiched between the glass is a layer of liquid crystals.Behind the back panel is a fluorescent light source that tries to get through the two misaligned panels of glass.In the default state, the light is blocked, and the panels appear black.Unless there is a light behind the panel or a very bright light reflecting through the front panel and then off the back panel, an LCD cannot display anything.
21 LCD MonitorsThe LCD monitors use the CMY (cyan, magenta, yellow) process of building colorsTriads of three crystals (each being able to pass only one primary color) are put together in a matrixBy turning on one of the crystals in each triad the same effect can be produced as with an electron beam and phosphorus in the CRT monitors
22 LCD MonitorsEach liquid crystal is in a matrix or grid (rows and columns) with very thin wires leading to a set of of switches along the top and side edges of the glass panelsWhen electric current is sent to a specific X-Y location on the grid, the liquid crystal is activatedLCD monitors can be passive matrix or active matrix
23 LCD Monitors Passive Matrix One transistor switch per row and column That is, for an 640x480 VGA LCD panel, the monitor requires 640 transistor switches along the side and 480 transistor switches along the top to produce the 640x480 pixels or dots of light
24 LCD Monitors Active Matrix The fundamental difference between the passive matrix and the active matrix is the number of transistor switches on the panel:The active matrix gives every liquid crystal its own switch.This speeds up the process of pinpointing a specific X-Y co-ordinate and also provides greater control over the crystal.
25 LCD Monitors The three main types of active-matrix LCD panels are: TFT - Thin Film TransistorsMIM - Metal-Insulator-MetalPALC - Plasma Addressed Liquid Crystal
26 Maximum Resolution and Dot Pitch Dot Pitch is the measure of how much space there is between a display's pixels. When considering dot pitch, remember that smaller is better. Packing the pixels closer together is. fundamental to achieving higher resolutionsResolution refers to the number of individual dots of color, known as pixels, contained on a display. Resolution is typically expressed by identifying the number of pixels on the horizontal axis (rows) and the number on the vertical axis (columns), such as 640x480
27 ResolutionFor both monitors and printers we are interested in the resolution – how small are the pixels (tiny dots)?Typical monitors have 640 480 or 800 600 with a screen size of inches (measured diagonally).For printers the resolution is in pixels or dots per inch, typically 600 dpi for a laser printer.
28 Refresh RateIn monitors based on CRT technology, the refresh rate is the number of times that the image on the display is drawn each second.Refresh rates are very important because they control flicker, and you want the refresh rate as high as possible.Too few cycles per second and you will notice a flickering, which can lead to headaches and eye strain.
29 Color DepthThe combination of the display modes supported by your graphics adapter and the color capability of your monitor determine how many colors can be displayed.For example, a display that can operate in SVGA mode can display up to 16.8 million colors because it can process a 24-bit-long description of a pixel. The number of bits used to describe a pixel is known as its bit depth.With a 24-bit bit depth, 8 bits are dedicated to each of the three additive primary colors -- red, green and blue. This bit depth is also called true color because it can produce the 10,000,000 colors discernible to the human eyeSimply put, color bit depth refers to the number of bits used to describe the color of a single pixel. The bit depth determines the number of colors that can be displayed at one time
30 16,777,216 (True Color + Alpha Channel) Color Depth ChartBit-DepthNumber of Colors12 (monochrome)24 (CGA)416 (EGA)8256 (VGA)1665,536 (High Color, XGA)2416,777,216 (True Color, SVGA)3216,777,216 (True Color + Alpha Channel)2
31 Things to ConsiderDisplay technology - Currently, the choices are mainly between CRT and LCD technologies.Cable technology - VGA and DVI are the two most common.Viewable area (usually measured diagonally)Aspect ratio and orientation (landscape or portrait)Scan or Refresh RateInterlace FeaturesDot pitchResolutionColor depthAmount of power consumption
32 Features Two measures describe the size of your display: The aspect ratio and the screen size.Aspect Ratio: Most computer displays, like most televisions, have an aspect ratio of 4:3This means that the ratio of the width of the display screen to the height is 4 to 3.Screen SizeHow to MeasureDesktop vs. Laptop
33 Features Scan or Refresh Rate, or vertical scan rate The time it takes for the electronic beam to fill the screen with lines from top to bottomThe number of times that the image on the display is drawn each second.If your CRT monitor has a refresh rate of 72 Hertz (Hz), then it cycles through all the pixels from top to bottom 72 times a second.Control flickerYou want the refresh rate as high as possibleStandard rate established by the Video Electronics Standards Association (VESA) is 70Hz, or 70 refreshes per second
34 Features Multiscan Interlace features Multiscan monitors support a variety of refresh rates and can support different video cardsFixed frequency monitors only support a single refresh rateInterlace featuresInterlaced monitors draw a screen in 2 passes, hitting the even lines first, then the odd linesNon-interlaced monitors draw the entire screen in 1 pass
35 Features Dot Pitch The distance between adjacent dots on the screen. The smaller the dot pitch, the higher the quality of the image.A high-quality monitor should have a dot pitch of no more than .28mmA display normally can support resolutions that match the physical dot (pixel) size as well as several lesser resolutions.For example, a display with a physical grid of 1280 rows by 1024 columns can obviously support a maximum resolution of 1280x1024 pixels but it usually also supports lower resolutions such as 1024x768, 800x600, and 640x480.
36 MonitorsResolutionA measure of how many dots on the screen are addressable by softwareEach addressable location is called a pixel (picture element)Most monitors offer a resolution of 1024 x 768 or higherThe video controller card as well as the monitor must be capable of supporting the chosen resolution.Resolutions are set from the Control Panel in Windows 9X
37 FeaturesColor DepthThe combination of the display modes supported by your graphics adapter and the color capability of your monitor determine how many colors can be displayed.Bit Depth : The number of bits used to describe a pixel is known as its bit depth.For example: with a 24-bit bit depth, 8 bits are dedicated to each of the three additive primary colors -- red, green and blue. This bit depth is also called true color because it can produce the 10,000,000 discernible colors.
38 16,777,216 (True Color + Alpha Channel) Bit-DepthNumber of Colors12 (monochrome)24 (CGA)416 (EGA)8256 (VGA)1665,536 (High Color, XGA)2410,000,000 (True Color, SVGA)3216,777,216 (True Color + Alpha Channel)
39 Features Power consumption Varies greatly with different technologies. CRTs are somewhat power-hungry, at about 110 watts for a typical display, especially when compared to LCDs, which average between 30 and 40 watts.Green monitorIn a typical home computer setup with a CRT-based display, the monitor accounts for over 80 percent of the electricity used!Monitor that meets the EPA Energy Star programUses 100 to 150 watts of electricity with no more than 30 watts being used when the screen saver is on
40 Some Features of a Monitor MonitorsFeature DescriptionScreen Size Typically 14, 15, 17 or 21 inch - refers to diagonal length of the lighted screen. It is often shorter than advertised.Refresh Rate Vertical scan rate - time it takes an electronic beam to fill screen. Should be minimum of 70Hz (70 times/sec.)Interlaced Only refreshes half the screen on every pass.Dot Pitch Distance between adjacent dots. Ex: .28mm The smaller the pitch, the higher the quality.Resolution How many spots or pixels are on screen. Ex: 640 x 480Multiscan Monitors that offer a variety of refresh rates.Green Monitor Supports EPA Energy Star program, uses no more than 30 watts and can go into sleep mode after inactivity.Some Features of a Monitor
41 Monitors ELF (extremely low frequency) emissions When matching a monitor to a video card, consider matching a14-inch monitor with a low-end video card15-inch monitor with a midrange card17-inch or larger monitor with a high-end card for best performance
42 Display Adapter or Graphics Card Creates and holds the image informationOlder technology: specialized circuitry on the system boardNewer technology: a Plug-In Card - often referred to as the PC’s Video CardGraphics cards are known by many names, such as:Video cardsVideo boardsVideo display boardsGraphics boardsGraphics adapter cardsVideo adapter cardsGraphics Accelerators
43 Display Adapter Standards IBM original: MDA - Monochrome Display AdapterMGA - Monochrome Graphic AdapterCGA - Color Graphics Adapter1981 – IBM - 4 colorsEGA - Enhanced Graphics AdapterIBM integrated color and monochrome systems – 16 colors
44 Display Adapter Standards VGA - Video Graphics ArrayIBMVGA became the industry standard and further extensions were developed:SVGA - Super VGAAVGA - Accelerated VGA - supports Windows GraphicsXGA – Extended Graphics ArrayIBM
45 Display Adapter Standards UXGA - Ultra Extended Graphics ArrayMost displays sold today support the UXGA standard.UXGA can support a palette of up to 16.8 million colors and resolutions of up to 1600x1200 pixels, depending on the video memory of the graphics card in your computer
46 Display Adapter Standards A typical UXGA adaptertakes the digital data sent by application programsstores it in video random access memory (VRAM) or some equivalentuses a digital-to-analog converter (DAC) to convert it to analog data for the display scanning mechanismOnce it is in analog form, the information is sent to the monitor through a VGA cable.
47 Display Adapter Standards DVI – Digital Video InterfaceSince today's VGA adapters do not fully support the use of digital monitors, a new standard, Digital Video Interface (DVI) has been designed for this purpose.DVI keeps data in digital form from the computer to the monitor, virtually eliminating signal loss (degradation).Will need a DVI monitor with a DVI compliant graphics card.
48 Graphics/Video Card An expansion card responsible for Receiving data and instructions from the CPUProcessing the dataSending the results to the monitorTwo main features of a video cardThe bus it uses (influences speed and performance)Amount of video RAM it has or can support
49 Four basic functions of a video card Graphics/Video CardFour basic functions of a video card
50 Video Card Performance Performance on the video card is affected by:Chip setMemoryRAM DACBus speed and sizeMethods of improving performanceDual-portingPlace a processor on the video card to make it a graphics accelerator
51 Graphics AcceleratorA type of video card that has its own processor to boost performanceNecessary with the demands that graphic applications make in the multimedia environmentProcessor is specifically designed to manage video and graphicsTheir features reduce the burden on the system board CPU and perform the function much faster than the system board CPU
52 Graphics Accelerator Features MPEG decoding3-D graphicsDual portingColor space conversionInterpolated scalingEPA green PC supportDigital output to flat panel display monitorsApplications support for popular high-intensity graphics software
53 Video MemoryNecessary to handle large volume of data generated by increased resolution and colorStored on video cards as memory chips
54 How Much Video Memory Is Needed? Determined byScreen resolution (measured in pixels)Number of colors (color depth)Enhancements to color information called alpha blending
55 Types of Video Memory VRAM (video RAM) MDRAM (multibank DRAM) SGRAM (synchronous graphics RAM)WRAM (Window RAM)3D RAM