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Video Adapters
The video adapter is the component that provides communications between the monitor and the system board. As with everything else, there have been several different standards over the years as follows:
| CGA |
640x200 |
| EGA |
640x350 |
| VGA |
640x480 |
| SVGA |
1600x1200+ |
SVGA is the current standard and is extensible which means that increased color depths and resolutions will be supported under the same SVGA standard.
Video cards contain their own RAM that allows them to support higher levels of color depth, resolution and performance. The Advanced Graphic Port (AGP) was developed to attain even higher performance levels including 3-D graphics rendering. AGP is derived from the PCI specification and is only used for video adapters. There are several AGP specifications that are listed in the table below:
| Mode |
Bus Speed |
Throughput |
| 1x |
66 MHz |
266 MBps |
| 2x |
66 MHz |
533 MBps |
| 4x |
66 MHz |
1.07 GBps |
| 8x |
66 MHz |
2.1 GBps |
The multipliers 1x, 2x, 4x and 8x refer to the number of times the signal is increased per clock cycle.
Further Reference:
http://www.techtutorials.com/Hardware/Video_Cards/
Video Displays
A video display(AKA Monitor) is based upon the use of an electronic screen called a cathode ray tube or CRT. The CRT is lined with a phosphorous material that glows when it is struck by a stream of electrons. This material is arranged into an array of millions of tiny cells, usually called dots. At the back of the monitor is a set of electron guns, which produce a controlled stream of electrons. These guns start at the top of the screen and scan very rapidly from left to right. Then, they return to the left-most position one line down and scan again, and repeat this to cover the entire screen. The electron guns are controlled by the video data stream coming into the monitor from the video card which varies the intensity of the electron beam at each position on the screen. This control of the intensity of the electron beam at each dot is what controls the color and brightness of each pixel on the screen. The entire screen is drawn in a fraction of a second.
Color monitors have 3 electron guns that control the display of red, green and blue light. The surface of the CRT is arranged to have these dots placed adjacently in a specific pattern. There are separate video streams for each color coming from the video card, which allows the different colors to have different intensities at each point on the screen. By varying the intensity of the red, green and blue streams, the full gamut of colors is achieved.
The surface of the CRT only glows for a small fraction of a second before beginning to fade. This means that the monitor must redraw the picture many times per second to avoid having the screen flicker as it begins to fade and then is renewed. The speed of this redrawing process is called the "refresh rate".
Monitor quality depends on the resolution, which is measure in pixels, or "dot pitch". Dot Pitch is a measurement of the distance between dots on the screen. The closer together they are the better the resolution. Dot Pitch is measured in millimeters.
There are several different types of displays available. LCD panels where previously only available for laptops, the prices have come down enough that they are now commonly used for desktop PCs as well. They are lighter, thinner, use less power and do not flicker like their CRT counterparts. Some flat-panel LCDs use a DVI connector instead of the tradition DB-15 connector used with CRTs.
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The monitor connects to the video adapter via a DB-15 connector on the board. Older video standards utilized a 9 pin connection. Some high performance monitors are connected via a BNC connection.
Laptops once used compact CRT based monitors, but now use Liquid Crystal Displays(LCD) because they are much lighter and compact.
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You should avoid exposing an LCD to extreme light, heat and cold.
Care should be taken when working inside monitors as they can contain electrical charges as high as 25,000 volts which is a potentially lethal amount.
Further Reference:
http://www.pcguide.com/ref/crt/index.htm
http://www.pctechguide.com/06crtmon.htm
Sound Cards
Your computer's sound card is responsible for taking sound data from a disk(like an MP3 file) and converting it so your computer's speakers can play it. Usually, this tweaking consists of changing digital ones and zeros into analog waveforms your ears can recognize.
The sound card is also responsible for doing it the other way around. It takes external sounds such as your voice as you talk into a microphone and converts those waveforms into ones and zeros so that they can be stored on a disk.
Sound cards are internal cards that are either built into the motherboard or are installed in an ISA or PCI expansion slot. The back of the sound card contains RCA jacks for connecting speakers and microphones.
If you want to be able to hear CDs playing in a CD-ROM drive through your sound card, you need to use an MPC2 cable to connect the CD-ROM drive to the sound card.
Most problems with sound are pretty easy to figure out. If you are having a problem getting sound, check the following items: Make sure that the speakers are on and the volume is turned up enough on the speakers. On the computer, make sure that volume in Windows is turned up and not muted. Make sure that your speakers are plugged into the correct RCA jack on the sound card. Check the device manager and make sure that there are no resource conflicts with the sound card.
Further Reference:
http://www.techtutorials.com/Hardware/Sound_Cards/
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