Introduction to CAAD
1. Graphic Cards
Graphic cards are hardware devices that help the computer process faster and more efficiently graphical information, such as colors or pixels on the screen, video signals, or 3D transformations. There are three types of graphic cards:
Graphics cards are usually in the form of a silicon card that connect internally with the computer's main processing card (motherboard) through a connectors. There are two types of connector: PCI and AGP (Accelerated Graphics Port). The difference between in the two connectors applies mainly to the speed of the connection. in general, AGPs are faster than PCIs. graphic cards are connected internally inside the computer as shown in the scheme below:
The cards may have different input/output connectors. The output connector to the monitor is called 15-pin and comes in compact (5x5x5) for PCs or flat (7x8) for Macs. Video signals are handled though RCA connectors or S-Video.
2. Video (VGA ) Cards
VGA cards in general handle colors and pixels. they determine the amount of pixels on the screen and the number of colors. They depend on video memory (VRAM) to increase the size and color information. Every computer has as its manufacturing settings a minimum screen resolution (640x480) and a minimum numbers colors (256) in order to display information. VRAM adds to that memory to increase the number of pixels and the number of colors.
Every pixel on the screen is associated with a set of bits (8-, 24-, 32-bits). A combination of bits (0s and 1s) determines the displayable colors. For example an 8-bit pixel can have 2 to the 8th = 256 possible bit combinations, therefore 256 different colors. A 24-bit will have 2 to the 24th = 16,777,216 possible bit combinations.
In computer languages every color can be denoted as a combination of 3 basic colors (Red, Green and Blue). Red would be (255,0,0), Green (0,255, 0), and Blue (0,0,255). (The reason why it is 255 and not 256 is because we start counting from 0). White would be (255, 255, 255) and black (0,0,0). Any other color would be a combination of RG and B.
Monitor screen are measured in diagonal lines (15", 17", 20"). The average screen today (1998) is 17'. Costs are around $300 for 17" and about $1,000 for a 20" screen. VGA cards vary between $50 to $200 and VRAM costs and average of $20 per MB.
3. Video Capture Cards
Video capture cards basically convert TV signals into computer RGB signals and vice versa. Their price and success is measured in size of display, format, and speed of motion. The basic setup of a video capture is as follows:
The prices of video capture cards vary according to their capabilities. Thing to consider are size of screen capture area, full-motion, number of colors, output formats. for example, in the following video card types:
| Miro DC-10 (230x640) $200 |
| Miro DC-20 (640x480) $600 TV screen = 570x570 |
| Miro DC-30 (640x480) $800 |
the less the money the less capture area. Also the DC-30 has beta output format and comes with more software.
4. 3D Accelerators
3D accelerators are special hardware cards that increase the speed of 3D movements. They plug-in to the motherboard as PCI or AGP and they take care of special calculations. Mostly these caluclations are mathematical and trigonometric. For example, a simple rotation of an object requires a set of sinus and cosinus calculations as shown below:
newx = x*cos(angle) - y* sin(angle) newy = x*sin(angle) + y* cos(angle)
every sinus of cosinus functions requires over 30 operations (+,-,*,/) to come up with a result. But if the sinus and cosinus of all possible angles (360) were pre-calculated and stored in memory, only one fetching operation would be required. instead we would need extra memory space to store all those possible sinus/cosinus values. In other words we trade calculations for memory. 3D accelerators are basically memory storage that stores angles indexes, pixelmaps, texture images, etc. making it easier for the computer to handle 3D movements.
Some of the graphics cards available (in 1998) are usually classified into categories: low, medium, high. For example:
| Company | Low | Medium | High |
| ELSA Gloria | Synergy | L/MX | XL |
| Oxygen | 102 | 202 | 402 |
| Diamond GL | 1000 Pro | 3000 | 4000 |
| Accel | Star | Eclipse | |
| Prices | $2-300 | $1-200 | $2-3000 |
References
Exercises
Quiz
1) What does PCI stand for?
2)
Answers
PCI stands for P