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Objectives Objectives Explain how video displays work Explain how video displays work CRT and LCD monitors Understand the concept of resolution Understand the concept of resolution Explain refresh rates and how they affect monitors Explain refresh rates and how they affect monitors Select the proper video Card Select the proper video Card Graphics Processor Video Memory 2

Introduction The term video encompasses a complex interaction among numerous parts of PC, all designed to put a picture on the screen. Video consists of two devices—the video card (display adapter) and the monitor (Video displays) 3 Monitor Video card

Video Card The video card consists of two distinct components One takes commands from the computer and updates its own onboard RAM The other scans the RAM and sends data to the monitor Video card Therefore Video card : handles all communications between CPU and monitor. BIOS OS needs to know how to handle communication between CPU and display adapter, which requires BIOS. 4

5 Monitors

CRT Monitors CRT is Cathode Ray Tube (CRT), which is type of a vacuum tube. slender One end of this tube is a slender cylinder that consists of three electron guns. wide The wide end of the CRT is the display screen. 6

CRT Monitors The inside of the display screen has Phosphor coating. When power is applied to one or more of the electron guns, a stream of electrons shoots towards the display end of CRT. yoke This stream is subjected to a magnetic field generated by a ring of electromagnets called a yoke that controls the electron beams point of impact. 7

CRT Monitors as visible light The phosphor coating releases energy as visible light when struck by the electrons. Phosphors continue to glow momentarily after being struck by electron beams—quality of phosphors is called persistence smeary Too much persistence and the image is smeary flicker Too little persistence and the image appears to flicker. 8

CRT Refresh Rates raster line How many line in screen? Video data is displayed on the monitor starting at the upper-left corner of the monitor ending to the lower- right corner. Each line are called raster line. How many line in screen? Horizontal refresh rate (HRR) Horizontal refresh rate (HRR) The speed at which the electron beam moves across the screen and to be ready for the next line. Vertical refresh rate (VRR) 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.

CRT Refresh Rates The Monitor does not determine the HRR or VRR. Video cards push the monitor at a given VRR, and then the monitor determines the HRR If the VRR is set too low, you’ll see flicker If it is set too high, you’ll have a distorted screen image and may damage the monitor. Multisync Multisync (multiple-frequency monitor) monitors support multiple VRRs.

Phosphors 12 Phosphors are dots inside the CRT monitor that glow red, green, or blue when an electron gun sweeps over them. CRT has three electron guns one for read Phosphor, one for green Phosphors and one for blue Phosphors. The higher the intensity of the electron stream the higher the color produced by Phosphors.

Phosphors 13 How we can prevent the red electron beam from “bleeding over” and lighting neighboring blue and green dots? How we can prevent the red electron beam from “bleeding over” and lighting neighboring blue and green dots? Shadow mask is a screen that enables only the proper electron gun to light the proper phosphor. The area of phosphors lit at one time by a group of guns is called a picture element, or pixel

Phosphors 14 Triad at least A pixel consists of at least 3 phosphor dots

Resolution Horizontal Pixel times Vertical Pixel Resolution is always shown as the number of Horizontal Pixel times the Vertical Pixel. A resolution of 640 X 480 means: Number of horizontal pixel is 640 and vertical pixel is 480. What does it means? If you multiply the values together you get ? What does it means? Resolution affecting the pixel size. 15

Common Resolutions 640x480 = 307,200 pixels per screen 800x x x x x1200 Most of these resolutions matches a 4:3 ratio (called aspect ratio) Many monitors (wide-screen monitors) have 16:9 or 16:10 ratio. Ex. 1366x768 and 1920x

Resolution  Maximum possible resolution  Maximum possible resolution: Determined by how small can one pixel be.  Theoretically, a triad, but various limitations in screens, controlling electronics, and electron gun technology make smallest pixel much bigger than one triad. 17

Dot Pitch Dot pitch Dot pitch—diagonal 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

19 LCD monitors Use Liquid crystal displays Have many advantage over CRT: Thinner and lighter. Much less power. Flicker free. No harmful radiation. flat panels flat panel displays Called flat panels or flat panel displays.

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Video Cards Video cards Video cards are composed of two major pieces : Video RAM Video RAM to store video image. Video processorGPU Video processor- GPU which takes information from video RAM and shoots it out to the monitor. Video card need fan to cool their onboard processor. Monitor plugs into the video card. 21

Color depth Each pixel in screen has color This color are stored in video RAM using tiny number of bits depend on the number of color you want. i.e. to get 256 colors, each pixel would have to be represented with 8 bits. Color depths determined by bits per pixel 2 colors = 1 bit (mono) 2 colors = 1 bit (mono) 4 colors = 2 bits 4 colors = 2 bits 16 colors = 4 bits 16 colors = 4 bits 256 colors = 8 bits 256 colors = 8 bits 22

Color depth Windows XP offers 32-bit color. 23

Video RAM Requirements Depends on Resolution + Colour Depth 24 Example: 1024 x 768 = pixels per screen bit bytes 32 bit colour = 4 bytes per pixel. 4 x = bytes. = 3 megabytes per screen.

Video Modes Your video card and monitor are capable of showing Windows in a fixed number of different resolutions and color depths. The choices depend on the resolutions and color depths the video card can push to the monitor and the amount of bandwidth your monitor can support. mode Any single combination of resolution and color depth you set for your system is called a mode. 25

Video Modes VGA 26 Video Graphics Array 640 x Color Supported 640 x 480 pixels and 16 Color. Check Your PC? Every video card made in the last 15 years can Output as VGA, but VGA-only cards are now obsolete. Check Your PC? Minimum display requirement by many software package.

Video Modes Beyond VGA Beyond VGA SVGA, XGA, and more 27 Typical DeviceAspect ratio ResolutionMode PDA and small video player 4:3320x240QVGA Small monitors4:3800x600SVGA Monitor and portable projector 4:31024x768XGA Small widescreen laptop16:101280x800WXGA LCD monitors5:41280x1024SXGA Widescreen laptop16:101440x900WSXGA

Motherboard connection Data moving from video card to display has to go through the video card’s memory chips and expansion bus and this can happen only so quickly. PCI, AGP, PCIe The standard PCI slot transfers 32 bits at speed 33 Mhz, yielding a max. bandwidth of 132 MBps. This may be enough until you use higher resolution, higher color depth and higher refresh rate. 28

A typical display at 800x600 with 70 HZ refresh rate and 8 bit color depth. How much data per second has to be sent to the display? A typical display at 800x600 with 70 HZ refresh rate and 8 bit color depth. How much data per second has to be sent to the display? 800 x 600 x 1 byte x 70 = 33.6 MBps MBps Using 24-bit color, the amount of data sent jumps to MBps. Although 132 MBps of PCI looks sufficient, but most systems have more than one PCI device each requiring part of this throughput. 29 Motherboard connection

AGP Intel answered the desire for video bandwidth even higher than PCI with Accelerated Graphics Port (AGP) single AGP: a single special port similar to PCI slot dedicated to video. It is derived from the 66-MHz, 32- bit PCI 2.1 spec. strobing It uses a function called strobing that increases the signals 2, 4, and 8 times for each clock cycle (called AGP x1, x2, x4, x8) 30

AGP cont. AGP has several technological advantages over PCI: It resides alone on its own personal data bus connected directly to Northbridge. It takes advantages of pipelining commands similar to CPU pipelining. sidebanding It has a feature called sidebanding: a second data bus that enables video card to send more commands to northbridge while receiving others at same time. 31

Accelerated Graphics Port 32

PCIe PCIe developed to replace PCI and AGP. PCI and AGP are using a parallel interface. It is a natural evolution for video as it is incredibly fast, using serial communication method. All PCIe video cards use PCIe x16 connector 33

Graphics Processor Unit (GPU) The most important decision in buying a video card is the graphics processor and amount of RAM onboard. The graphics processor handles the heavy lifting of taking commands from the CPU and translating them into coordinates and color information that the monitor understands and displays. Graphics Processor

Most video processors are made by: – NVIDIA – ATI Radeon X1950 XTX 512 ATI Radeon X1950 XTX 512 MB – ATIManufacturer – Radeon X1950 XTXProcessor & Model No. – 512 MBAmount of RAM Graphics Processor

NVIDIA and ATI release multiple models of graphics processors each year Most features only seen in 3-D games – Textures – Transparency – Shadows – Reflection

Video Memory Video RAM constantly updates to reflect every change that takes place on the screen Different video modes require different amount of memory. DRAM slower but cheaper VRAM is specialized Video RAM more expensive but faster. It can read and write data at same time 37

Video Memory WRAM (Window RAM) is slightly faster than VRAM but not as widely accepted SGRAM (synchronous graphics RAM) is sync-ed to the system clock Now DDR SDRAM is used. 38