Video Cards

1
Video Cards

• CS431 Class Presentation
• Ashish Bhat (02007025)
• Nilesh Meshram (02007027)

2
Introduction

• Interface between computer and a display device
• Unless a computer has graphics capability built
  into the motherboard, the video card is required.
  
• The CPU, working in conjunction with software
  applications, sends information about the image
  to the video card. The video card decides how to
  use the pixels on the screen to create the image.
  It then sends that information to the monitor
  through output interface.

3
The Evolution of Video Cards

• IBM introduced the first video card in 1981
  called a Monochrome Display Adapter (MDA), which
  provided text-only displays of green or white
  text on a black screen.
• Presently, the minimum standard for new video
  cards is Video Graphics Array (VGA), which allows
  256 colors.
• With high-performance standards like Quantum
  Extended Graphics Array (QXGA), video cards can
  display millions of colors at resolutions of up
  to 2040 x 1536 pixels.

4
Components in a Video Card

• Graphics Controller / Graphic Processing Unit
  (GPU)
• Video Memory (RAM)
• Digital-to-analog Converter (DAC)
• Attribute Controller
• Output Interface - RGB, Composite, DVI
• BUS Interface
• BIOS

5
Components in a Video Card
6
Video Card - GPU

• Similar to CPU but designed specifically to
  perform complex mathematical and geometric
  calculations necessary for graphics rendering
• Less congestion on the system bus
• Reduction in the workload of CPU

7
Video Card - GPU

• Operations bitmap transfers, painting, window
  resizing and repositioning, line drawing, font
  scaling and polygon drawing etc.
• Some GPUs have image enhancement algorithms
  built-in
• e.g. 3D edge smoothening

8
Video Card - GPU

• Some of the latest GPUs have more transistors
  than average CPU and produce a lot of heat.
  Heat-sinking and fan cooling are required

9
Video Card - Memory

• Video Memory (RAM) is used for
• Frame Buffering holding completed imaged until
  its time to display them
• As the GPU creates images, the image information
  is stored in this video memory frame buffer as a
  digital bitmap
• Total amount of video memory installed may not be
  needed for a particular resolution, the extra
  memory often used for caching information for the
  graphics processor
• for example, the caching of commonly used
  graphical items, such as text fonts and icons

10
Video Card - Memory

• Unified memory architecture Use of portion of
  system memory as frame buffer
• - Cost reduction
• - Inferior graphics performance
• The greater number of colors, or higher the
  resolution, the more video memory will be
  required.
• However, since it is a shared resource reducing
  one will allow an increase in the other

11
Video Card - DAC

• RAM connects directly to DAC
• known as RAMDAC
• Used to convert the digital image information
  stored in video memory into analog signals that a
  monitor can use
• The range of refresh rates decided by
• - The rate at which the RAMDAC converts the
  information
• - The design of the graphics processor
• Multiple RAMDAC

12
Video Cards - Resolution and Color depth

• Resolution
• - specified in terms of a row by column figure
• - the maximum number of displayable pixels
• - determined by the beam size and dot pitch
• - refers to the sharpness, or detail of the
  visual image
• Color Depth
• determined by the intensity of three beams of
  light (Red, Green and Blue) and the amount of
  information stored about a pixel
• Different Modes
• 8 Bit 256 Color Mode
• 16 Bit High Color mode
• 24 Bit True Color Mode

13
Video Card - Attribute Controller

• Contains the Color Look-up-table (CLUT) which
  determines which color will be displayed for a
  given pixel value in the video memory
• Used when the display mode is not true color
  (24bit or 48bit). In such cases the most used
  colors are stored in this CLUT
• Dithering
• - uses two colors to create the appearance of a
  third
• - gives a smoother appearance to abrupt
  transitions

example color palette
14
Video Cards Resolution and Colors
15
Output Interface - RGB

• Most CRT monitors require signal in analog form.
  This interface is known as RGB interface
• This interface has three separate lines for the
  red, green and blue color signals, and two lines
  for horizontal and vertical sync signals
• CRT controller in the video card generates
  horizontal and vertical sync signals

16
Output Interface - Composite

• Composite video interface is used in Television
• First RGB data is converted into chrominance
  (color) and luminescence (intensity) signals and
  then both are time multiplexed with horizontal
  and vertical sync signals to give a single
  composite video signal

17
Output Interface - DVI

• LCD Monitors work in digital mode and require
  display data in digital form
• RAMDAC is thus bypassed and data is sent directly
  in digital form. This interface is known as DVI
  (Digital Video Interface)

Output interface requirement for different
monitors
18
Video Card - BUS Interface

• ISA Interface (Obsolete)
• PCI Interface (Obsolete)
• AGP Interface
• PCI Express Interface

19
AGP Interface

• AGP Accelerated Graphics Port
• Single dedicated Point-to-point Connect
• Pipelined transfers
• Video RAM Sharing
• Being replaced by new PCI Express

20
Video Card - BIOS

• Initialization of hardware setting during boot-up
• Provides a set of standard routines to control
  and use the video card
• e.g. change display mode, gotoxy, change color,
  write text etc.
• traditionally video cards were built according to
  certain standards (CGA, VGA, SVGA etc.) and
  provided the same functionality through these
  standard routines.

21
Video Card Interfacing

• Older video cards provide a set of standard
  routines accessed through BIOS
• Display Drivers

22
Video Card Interfacing in Windows
23
References

• http//www.howstuffworks.com
• http//www.pctechguide.com/
• http//www.epanorama.net

24
Thank you!
25
Video Card Types of Memory

• Standard DRAM Used in earlier system
• Video memory implementation on graphics board
• - VRAM
• - WRAM
• - EDO
• - SDRAM
• - DDRRAM
• - RDRAM