The image on the display screen consists of tiny dots called pixels. With the most common Full HD resolution, their number exceeds 2 million, and the PC must decide what to do with each of them. To do this, you need an intermediary that could convert binary data into a visible image. If the computer does not cope with this task using the hardware of the motherboard, a graphics card takes care of it.
The calculations are complicated, but the device and the principle of the video card is easy to understand. This article discusses its main components, their functions, as well as factors, the combination of which ensures high PC performance and efficiency.
How does a video card work?
A computer can be represented as an organization with its own art department, to which a request is sent to paint a picture. The department decides what the drawing should be and then puts it on paper. In the end, someone's idea is realized in a visible image.
The principle of the video card is the same. The processor and software transmit information to a graphics card, which decides what the pixels on the screen should be to get the desired image. Then this data is sent via cable to the monitor.
Creating an image from binary numbers is difficult. To display a three-dimensional picture, the graphic card must first calculate the frame from straight lines. Then she fills it with pixels. After that, color, lighting and texture are added. In high-speed computer games, the graphics processor must perform all these calculations at least 60 times per second. Without it, the CPU load would be too great.
The operation of a computer video card, in principle, depends on the following 4 main components:
- connections to the motherboard through which power and data are supplied;
- a processor that processes each screen pixel;
- graphic memory storing data about each pixel and completed images;
- systems for displaying the final result.
GPU
The principle of operation of video cards is based on obtaining data from the GPU and converting them into images.
Like a motherboard, a graphics card is a printed circuit board with a processor and RAM. It is also equipped with a microchip of an input-output system (BIOS), in which settings are stored and which, at startup, diagnoses the operation of memory, input and output systems.
The graphics processing unit is similar to a computer's CPU. However, the GPU is specifically designed to perform the complex geometric and mathematical calculations that are needed for image rendering. Some of the fastest processors have more transistors than the average CPU. GPU generates a lot of heat, so it is usually cooled by a radiator or cooler with a fan.
In addition to the huge processing power, graphic processors for analysis and data use interact with special software. The companies nVidia and ATI release the vast majority of chips for video cards. They develop their own means of increasing productivity. To achieve higher image quality, GPUs use:
- full-screen smoothing of the edges of 3D objects;
- Anisotropic filtering for enhanced video clarity.
While maintaining the general principle of video cards, each manufacturer develops their own techniques for coloring, applying shades, textures and patterns.
Since the GPU creates images, it must store them somewhere. For this, an online storage device is used. It stores information about all the pixels, their color and location. Part of the RAM can also function as a frame buffer with completed images until it is time to display them. As a rule, the memory operates at a very high speed and is bidirectional, i.e., the system can read and write data at the same time.
Graphic RAM is directly connected to the digital-to-analog converter of the DAC, which converts the image into a signal used by the display. Some video cards have several such modules, which improves performance and allows you to support more than one monitor.
The DAC sends the final image over the cable. The principle of operation of a video card with interfaces is described in detail below.
PCI slot
Graphics cards are connected to the computer through a connector on the motherboard. Power is supplied through it and data is exchanged with the processor. Powerful video cards often use more power than the motherboard allows, so they are equipped with a connector for direct connection to the power supply.
The connection is usually made through the interfaces PCI, AGP and PCI Express (PCIe). The latter is the most modern and provides the highest data transfer speed between the card and the motherboard. PCIe supports the use of multiple graphics accelerators simultaneously.
The principle of the video card: monitor connection
Most graphics cards allow you to display an image on 2 displays. The connection is made via the DVI, HDMI, DisplayPort ports, which support LCD monitors, and VGA, to which CRT-type screens are connected. Some cards have 2 DVI ports. But this does not exclude the possibility of using cathode ray tubes, since they can be connected through an adapter. Apple previously manufactured monitors with the proprietary ADC connector, which was replaced by a DVI port, and then a USB-C-based Thunderbolt, backward compatible with HDMI and DisplayPort.
Most use only one display. Those who need 2 monitors can purchase a graphics card with the ability to display two screens. Such PCs can support 4 or more displays.
Other compounds
In addition to the motherboard and monitor, some graphics cards allow you to connect to:
- TV display (via TV-out or S-video output);
- analog video cameras (via ViVo and video input);
- digital cameras (via USB or FireWire).
Separate video cards are equipped with teletyuners.
DirectX and Open GL
API application programming interfaces provide effective interaction between programs and hardware, providing simple means of performing complex tasks (for example, three-dimensional visualization). Developers optimize graphics games for specific APIs. This is why the latest games often require updating versions of Open GL and DirectX.
APIs differ from drivers, which are programs that enable hardware to work with the computer OS. However, updating drivers can also ensure the correct functioning of applications.
Evolution
Ever since IBM produced the first prototype in 1981, the operating principle of video cards has not changed. Then they were called monochrome display adapters. With their help, it was possible to display only text on a black and white screen. The minimum standard for graphics cards is VGA, supporting 256 colors. And thanks to high-performance standards like 4K UHD, millions of colors can be displayed on screen with a resolution of 3840 x 2160 pixels.
Video card selection
A good graphics card has a fast processor and a large amount of RAM. Often she looks very attractive. High-performance models feature a striking design with decorative fans and radiators.
High-performance graphics cards offer much more power than most users need. Those who use their PCs for reading email, word processing and web surfing will find everything you need in a motherboard with integrated graphics. Most intermittent gamers have a mid-range graphics card. Powerful graphics accelerators are needed only by computer game lovers and designers who are engaged in 3D-modeling.
The principle of operation of the video card in the laptop and PC is the same, although due to the lack of free space, the former externally differ from the latter. A good parameter for evaluating the performance of graphics cards is the frame rate. The human eye perceives about 25 fps, but for smooth animation in some games you need a speed of more than 60 fps. The frame rate is determined by:
- The number of triangles or vertices per second that make up three-dimensional images. This parameter describes the calculation speed of the entire polygon or vertices that define it.
- The pixel fill rate, which indicates how fast the GPU is able to rasterize the image.
Performance
The speed of the video card depends on the hardware. Its performance is most affected by the following specifications:
- clock frequency;
- memory bus width;
- RAM bandwidth
- RAM size and frequency;
- DAC frequency.
The CPU and PC motherboard also play a role, since even a very fast graphics card is not able to compensate for the poor performance of the system.
Integrated graphics
Many PCs are equipped with integrated graphics cards. The principle of operation of such graphics accelerators differs from discrete cards in that they share RAM with the CPU. They can easily handle two-dimensional images, so they are ideal for office and Internet applications. Installing a discrete card to such motherboards disables the integrated graphics functions.