3.5. Video controllers and monitors

Devices that display information on a monitor screen are called video adapters, or video controllers . The video controller is an expansion card that provides the formation of an image on the monitor screen using information that is transmitted from the processor.

Video controllers are connected to a PC using special local PCI or AGP buses. The AGP interface is used to speed up the exchange of data between the processor and the video card. Many video cards are designed to be connected to the motherboard via an AGP connector.

Information is displayed in text or graphic mode. In the text mode , a character image of the data on the monitor screen is used, and the image data is stored in the ROM. Images after powering on the computer are overwritten from ROM to OP. When working in graphics mode , a point-by-point display of information on the screen is used, with each point of the screen being simulated by a series of bits that characterize the color of each of the points depicted. In VGA mode, each point is defined by a sequence of four bits, so each point can be displayed in one of 16 = 24 possible colors. Simulation of the graphic screen can be done with different sets of points, both vertically and horizontally.

Modern video adapters are called graphics accelerators, since they have special chips that allow speeding up the processing of large arrays of video data. Also, these graphics accelerators are called accelerators, they have their own specialized microprocessor and memory. What is important is the amount of this memory, since it forms a complete graphical point-by-point image of the screen. In the course of its work, the video adapter uses its own memory, but not operational.

However, for high-quality image reproduction, it is not enough to have video memory of the required volume. It is important that the monitor can provide output in high-resolution modes and that the software that sets the imaging can support the appropriate video mode.

Desktop computers use monitors on cathode-ray tubes, liquid-crystal monitors (LCD) and, less commonly, plasma monitors.

When working in graphic environments, you should use monitors with a screen diagonal of at least 15-17 inches. Among the main parameters of monitors are:

• maximum resolution;

• diagonal length;

• distance between pixels;

• frame rate;

• degree of compliance with environmental safety standards.

The image is considered better if the distance between the pixels is minimal and the frame rate is high. At a frequency of at least 75 Hz, an image comfort level for the eye is provided. The ideal sweep frequency is considered to be the frequency of 110 Hz, at which the image is perceived to be absolutely still. The frame rate is not a constant value, i.e., when working with higher resolution, the same monitor uses a lower frequency. The quality of the video adapter used also influences the image quality, since low-cost models may not support the appropriate frequency.

Personal computers use LCD- and TFT-displays, as well as displays with dual screen scanning. TFT displays are the most promising, but quite expensive. The resolution of TFT-displays is 640x480, and in more expensive laptops - 800x600 pixels and less often 1024x768.