Monitors and Video Cards Study Guide
Description: A video display system has 2 components: a display monitor and a video card. A
display monitor is a video output device capable of displaying text and graphics. Internal to the
monitor is the CRT (Cathode Ray Tube). A CRT is a display device in computer monitors as
well as television sets. A CRT consists of a glass vacuum tube that contains one electron gun for
a monochrome display, or three RGB (red, green, blue) electron guns for a color display.
Electron beams from these guns sweep rapidly across the inside of the screen from the upper-left
to the lower-right of the screen.
The inside of the screen is coated with thousands of phosphor dots that glow when they are
struck by this beam. The beams sweep rate is between 43 and 87 times per second (refresh
rate) and is measured in Hz (hertz).
Like televisions, screen sizes are measured in diagonal inches, the distance from one corner to
the opposite corner diagonally. Several sizes of monitors are available. The most common are the
14 or 15 inch monitor. There are also 17 and 21 inch monitors available.
FACTORS THAT AFFECT THE MONITOR TO DISPLAY A SHARP IMAGE:
RESOLUTION: The quality of the monitor's image is called the resolution. The resolution is the
degree of sharpness of a displayed or printed image. The more the resolution the more dots
there are on the screen. The resolution is measured by Dot Pitch and Pixels.
Dot Pitch: The dot pitch is the width of the dots (measured in millimeters) that the monitor
can display. The dot pitch is the distance between two like-colored phosphors in adjacent triads
or strips. Pixels are arranged in triads in conventional radius and flat square monitors and in
strips in Trinitron monitors. There are 4 common dot pitches for monitors: 0.34, 0.31, 0.28, and
0.26. As the dot pitch becomes smaller, the image on the screen will be sharper, the finer
details will appear on the screen, and color will be more vivid.
Pixels (Picture Element): A pixel is the smallest element that display software can use to
create text and graphics. Resolution of displays is measured in pixels. For example a display
resolution described as 640 X 480 has 640 pixels across the screen and 480 pixels down the screen for a
total of 307,200 pixels. The higher the number of pixels the higher the screen resolution.
INTERLACED VS. NON-INTERLACED: In the interlaced scanning mode the electron gun
makes 2 passes over the monitor screen, painting every other line on the screen on the first
pass and filling in the rest of the lines on the second pass. Interlaced scanning decreases the
sharpness of the picture. With high resolution graphics the effect is very noticeable.
Most computers use non-interlaced scanning REFRESH RATES: Today's monitors have vertical
which scans each line of phosphor dots
refresh rates in excess of 100 Hz, and multiple
consecutively providing the most clarity.
horizontal scanning frequencies, popularized with the
Research indicates that the scanning mode has NEC MultiSync monitors. A refresh rate of at least 70
an effect on the amount of eye fatigue caused Hz is recommended, while 85 Hz and above are
by computers. Therefore non-interlaced
exceptionally crisp. Using 60 Hz is insane in
monitors are the better choice, although they fluorescent lighting, and an interlaced refresh rate of
are a little more expensive. When considering 48 Hz is horrible.
eye fatigue, monitors with anti-glare coating
are best.
TYPES OF MONITORS:
Monochrome: This type of monitor can display only one color, or various shades of that one
color. In older monitors that were monochrome, the color may be white, green, or amber. In
others, the color may be black and white. Even though a monochrome system can be a color
other than white, they are still called black and white systems.
Color Monitors: A color monitor using the colors red, green, and blue can display up to 256
colors chosen from a palette of 262,114 colors.
CGA (Color/Graphics Array): This type of monitor was introduced by IBM in 1981. It
provides low resolution text and graphics. Resolutions: 640 X 200 with 2 colors; 320 X 200 with
4 colors. 9 pin digital RGB & NTSC (National Television System Committee) composite video.
EGA (Enhanced/Graphics Array): This type of monitor was introduced by IBM in 1984.
Resolution: 640 X 350 with 16 colors. 9 pin digital RGB.
VGA (Video Graphics Array): This type of monitor was introduced by IBM in 1987.
Resolution: 640 X 480 with a maximum of 256 colors. 15 pin analog RGB.
SVGA (Super Video Graphics Array): Resolution: Displays a resolution of at least 800 X 600
to a maximum resolution of 1600 X 1200 with from 16 to 16,777,216 colors displayed. 15 pin
analog RGB.
Many Mac monitors contain Sony Trinitron tubes, which use an aperture grill made of thin parallel
wires instead of a thin metal plate with holes in it. The Trinitron produces a sharper and brighter
image.
Rear of VGA Colored Monitor
VIDEO CARD
Your system's video card is responsible for what you see on your monitor screen. Besides video
cards, video may be integrated on the motherboard. Having it included on the motherboard
eliminates the possibility of choosing a card to meet your needs. Many have an option by jumper
or BIOS setting to disable the on-board video when updating and adding a true video
acceleration card. Usually this video does not render high resolution large screen graphics.
Otherwise, a graphic card has the following features:
Power Supply: The monitor is the only component of a regular PC that uses its own power
supply, built into the monitor itself. Older monitors often used a special plug that connected to a
receptacle at the back of the PC's power supply. This receptacle is just a pass-through from the
power cord that the PC uses - these monitors do not get power from the PC's internal power
supply.
Acceleration: Modern video cards have acceleration. Their video cards added smarts to enable
them to do much of the video calculating work that had been previously done by the main
processor. The video card becomes a coprocessor, working with the main CPU. New 3D
accelerators are becoming more common, which offload the (tremendously time-consuming)
work of 3D animation from the processor as well. Graphic cards today are accelerator cards.
Video Chipset: The video chipset on the cards is called the accelerator or video coprocessor.
How do identify Your Video Card.
Video BIOS: The video BIOS interfaces software to the video chipset in the same way that the
system BIOS does for the system chipset.
Video RAM: The video chipset is the brains of the video card and determines what its
capabilities are. The main use of the video memory is as the frame buffer. This is the place
where the information is stored about the video image itself. Each pixel on the screen has
associated with it typically 4 to 32 bits of data that represent its color and intensity. Video ram
comes in
DRAM
EDO RAM
VRAM (Video RAM - specifically designed for high resolution video systems)
WRAM (Windows RAM)
SGRAM (Synchronous Graphics RAM)
MDRAM (Multibank DRAM.
For more information, go to The PC Guide (video memory technologies).
The video processor, along with the system CPU, manipulates this data to change the screen
image and the RAMDAC reads it and sends it to the monitor.
RAMDAC (Random Access Memory Digital-Analog Converter): The screen image
information stored in the video memory (RAM) is digital, because computers operate on digital
numbers (sets of ones and zeros). The patterns of ones and zeros control the color and
intensity of every pixel (dot) on the screen.
The monitor, however, doesn't use digital information. It is analog. In order to display the image
on the screen, the information in video memory must be converted to analog signals and sent to
the monitor. The device that does this is called the RAMDAC.
PCI vs. AGP Video Cards: There are cards for a PCI slot as well as AGP (Accelerated
Graphics Port). AGP was designed by Intel in 1997, specifically for the video subsystem. It is a
new technology. It is considered a port not a bus. The idea behind AGP is to create a faster,
dedicated interface between the video chipset and the system processor. The interface is only
between these two devices. It makes it easier to implement the port, makes it easier to
increase AGP in speed, and makes it possible to put enhancements into the design that are
specific to video. AGP motherboards have a single expansion card slot for the AGP video card,
and usually one less PCI slot, and are otherwise quite similar to PCI motherboards. For more
information go to The PC Guide.
Video Drivers: Special drivers are written by the video card (or video chipset) manufacturer
for each operating system they support, which interface the operating system to the hardware.
The driver gives specific information between the hardware and the operating system so that
the video display card utilizes all that is incorporated within it, and so that it displays properly
on the monitor screen. Generic video drivers may or may not work for each individual video
display card. It is for this reason that you should try to deal with a manufactured card that is
well known. In addition to this, drivers are often updated by the manufacturer to fix bugs and
other incompatibilities.
Beware of OEM's: Using OEMs is the practice of cutting deals with video card (and other
computer component parts) manufacturers to purchase large quantities of lower-capability
video cards for their systems. (This appears to happen with video cards more than most other
components.) "While the retail version of a particular card may have certain performance
characteristics, the OEM version can have much worse performance. The difference in
performance between a retail and OEM version of the same card can be substantial, although
sometimes it is not. These OEM video cards are advertised using the full name of the video card
and there is no way to tell that what you are getting is not identical to the full retail version
unless you ask specifically when buying the system." (quoted from The PC Guide)