3.5.7. Graphics System

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The most important element of the graphical system is the graphics card. It is an electronic device that is most like the card through the slot includes the configuration PC. The basic circuit of the GRAPHICS CARD is a graphics processor - GPU (Graphics Processing Unit) which is charged with providing visualization of the activity of some kind of software or users on the monitor screen. Hence sometimes called VPU (Visual Processing Unit). More modern and cheaper solution containing less powerful GPU chipset in the composition of the computer or microprocessor. Analogous tasks, basic parts of the graphics card.

             1. Video controller - connection to the I / O bus
             2. Character generator ROM
             3. Video RAM
             4. Generator of RGBI video signals (signals and image intensity)
             5. Synchronization signal generator (HSYN and VSYN) for monitor

RGBI generator and synchronizing signal forming circuit management and monitor and control themselves, among other things contains circuitry conversion of digital data into analog signals (D/A conversion - DAC) and color table (palette) on the basis of which is determined from records digital color. Data table color and number of picture elements (resolution) are stored in the video BIOS.

All video control circuitry connects via an internal video bus. The more expensive cards can contain other devices like a TV tuner, VHS and SVHS video output and so on. Of course these are all port's belonging to the video card.

Basically may work with two groups of modes:

             I. Text modes
            II. Graphic modes

Text mode displays only the characters that gives the character generator and usually a representative of the character in a grid of 80 columns and 25 rows. Groups of the same character style called fonts. The number of columns and rows can be increased or decreased depending on the card capabilities. The appearance of the font is entered into the ROM card, and about his on-screen rendering care graphics processor.

Graphics mode is more demanding, because the finer shared on-screen display (resolution display of 320200 pixel and above) and can make text characters vary in shape and size (vector-scalable fonts). We can accept the interpretation that the image on the screen is divided into graphic and text file that may be necessary and displayed simultaneously. Today's card is essentially no separate text and graphics functions, but emulates text mode with the help of sophisticated video electronic circuits. Hence the possibility of scalability fonts - change the font size for discretion. Thus, the text mode in its original form is almost no longer exists because it successfully acts as the graphical environment. Character generator ROM is no longer significant. It will be used mostly to generate representations regarding adjusting the BIOS settings.

Features images stored in video memory (VRAM), usually faster than system memory, although cheaper versions for the same purpose using DRAM memory, the kind used for working memory. Organizations use these kinds of memory is not the same.

 Block diagram of Graphics Card
Figure* 3.5.18 Block diagram of graphics card with DRAM and VRAM. ( + / - )

Data in DRAM memory card alternated between a monitor control, memory and graphics processor or accelerator via internal bus video card, whereas the VRAM listed circuits connected sequentially allowing the VRAM simultaneously with one side connected to a monitor control on the other side of the graphics processor. Advanced version of DRAM for graphics cards is GDDR memory type, specially developed type of memory that is characterized by a large bandwidth and is technologically similar to DDR RAM memory for computers and somewhat suppresses VRAM, which is expensive and complex.

D/A converter has the task of converting binary representation of the analog signal to control the color and brightness of individual pixels on a monitor. Common name for the same DAC (Digital-to-Analog Converter), and since it is also the logic that manages the RGB color range for which the values read from the video memory is a common designation and RAMDAC. HV mark indicates that the same set of outputs and signals for monitoring deflection of the electron beam inside the cathode ray tube monitors horizontally and vertically.

Graphics card can be integrated with the motherboard (on-board), in the case of microprocessors, or as a standalone card inserted into the ISA (Industry Standard Architecture), PCI (Peripheral Component Interconnect), AGP (Accelerated Graphics Port), or PCI-Express slots on the motherboard. Separate cards that are inserted into slots motherboard computers typically use their own memory on the processing of video images, while other species use part of memory the computer for this purpose. For applications that use a word processor and a few graphics to meet your particular graphics card on the motherboard. No image processing or video is a discipline that the overall price of a computer can increase, particularly through price graphics card. ISA and PCI graphics cards already lengthy history, and the generally accepted concept of a PCI-Express card suppressed AGP solutions.

Of course, if the image is composed of several elements (higher resolution) and contains a richer color table is defined with more data and takes up more memory and slower to render, and the requirements for video memory depending on the mode and range from a few hundred kB to several GB, and a built-in D/A converters must operate at a higher frequency in order to get a larger amount of data to process. GPU (Graphics Processing Unit) that are installed on the graphics card you're often in the number of embedded elements 'more powerful' than microprocessors. Way of preparing images for display on the screen varies from manufacturer to manufacturer (ATI, nVidia, SiS ...), and a set of instructions that use. Coupling between the operating system (OS) and the card is a set of instructional programs, called drivers. Well written drivers are of great importance to the efficient operation of the graphics card. If the drivers can not take advantage of all the advanced features such GPU graphics card does not need to buy if you intend to use the computer for gaming. This situation can occur when the same GPU used by multiple manufacturers, the designer and his producer and his partners. Partners will offer a cheaper and simplified drivers, more powerful and original drivers for their cards will not work. So, payable mind.

I view it more closely resembles the process of displaying film stocks (scenes), each of which is divided into tiny triangles (polygons) that are individually painted. When we want to get a realistic impression of depth to the images, polygons that are 'closer' to draw larger and they're away 'plotted the net. Method that makes it possible is called the 'Z-buffer'. If a triangle has more details, and it is smaller, and if they are much more widely used in the construction scene, the picture is more realistic. The very image processing when all of the polygons ensembles includes terms like texturing, perspective correction, specular lighting, bilinear and trilinear filtering, mip maps, bump mapping, multitexturing, antialiasing, pixel and vertex shaders and lots of other things that are practicable only through GPU. Modern graphics cards can handle millions of polygons per second, which allows them to display screens present a very realistic picture. Word processing software (such as Word) does not require GPU demanding, but if it comes to games, the requirements in the design of graphics cards (and prices) are terrible. But because the dinosaurs look very convincing. Laughing, screaming and crying. More about the features of the graphics card is on the page that describes playing.

Jumper tab determine the initial parameters of the card and the monitor adjusted to the type and number of pieces and the size of memory card. Along with the card delivers software oriented to the major global software products (the driver) to enable the correct display of images on the screen to use DOS, Windows or Linux applications. PnP capabilities of new motherboards and graphics cards this procedure jumper setting by the user off.

The usual VGA/SVGA graphics card has 15 pin connector on the front card to connect the monitor to the card. Additional connections may exist for the already mentioned as possible additions to the card. Increasingly important role in the DVI (Digital Visual Interface) 29 pin connector through which the monitor can forward already mentioned analog (RGB) signal or a digital signal without the mediation of D/A converters, or both. Of course, the monitors must have the ability to choose, acceptance and processing of one of these signals in order to display the image on the screen. Another small detail for game lovers. PCI-Express standard in full the bus is about ways to access the graphics card and other devices, which means you can use two or more interrelated graphics cards simultaneously. Some manufacturers of chipsets and motherboards that incorporate two or more slots for graphics card consolidated special technology to work together more graphics cards and is dominated by two similar solutions SLI (Scalable Link Interface) or CrossFire. With multi-core processors provide a considerable 'power toy'.

To the displayed image is properly looked at the monitor, an important factor is the RESOLUTION and COLOR DEPTH. The term should be distinguished work RESOLUTION resolution and maximum (native) resolution monitors and graphics cards. If the monitor can display an image at the highest resolution 640480 pixels, the graphics card that can generate an image resolution of up to 20481536 pixels and can not be expected to score better than the original specified. CRT system is good to choose a monitor that has a native resolution equivalent highest resolution graphics card or higher. Then the number of physical pixel (triode) monitors participating in the representation of a single element of a larger image and display the image quality. With LCD monitors technological process of making them conditional on the view most appropriate when the resolution of the displayed image matches the native resolution for your monitor (native resolution), because otherwise the image of a 'smear'. Native resolution LCD monitor has a physical number of pixel horizontally and vertically integrated when creating monitors. This means that the different dimensions of the monitor to the user to choose the most appropriate native resolution. Not good at choosing diagonal LCD monitor 15" which is the native resolution of 16001200 is the letters in Windows so small that it is very tiresome work. At this detail to be taken when purchasing an LCD monitor or projector.

COLOR DEPTH is the number of shades of each color that can be achieved and that basically allows the graphics card. Each pixel, RGB or triode, can light a different color intensity, so that everything is digitized color range is defined by the number of bits available for each pixel (bpp - bits per pixel) when the number of bits multiplied by the number of pixels is images obtained by caching minimal size video graphics cards. GPU card handles color depth as follows:

              8 bpp = 256 colors
             16 bpp = 64K colors (65536) = High Color (Medium)
             24 bpp = 16.7M colors = True Color (Highest)
             32 bpp = 16.7M colors = True Color + 8 bit ALPHA CHANNEL

Alpha channel allows color correction adjacent pixel element when the edge of the object images do not 'fall' in full triode monitors, but is somewhat shifted. Then there is the color correction between adjacent pixel. This has great significance in the professional image processing. Considering the above, it can be calculated Cache size:

Image Resolution
Color Depth
640480 8 2'400
16 4'800
24 7'200
1024768 8 6'144
16 12'288
24 18'432
20481536 8 24'576
16 49'152
24 73'728

If you are yet to take into account that the general principle of modern graphics cards to one image while another prepares these values should be multiplied by two, and if using two-channel display system images (two VGA outputs) then these values should be multiplied by four.

Besides the above graphics card and its GPU and ACCELERATING the processing of the image display unit must pass to a considerable amount of information, especially when dealing with textures and 'triangles'. Thus, there is a serious problem 'to channel' data at higher resolutions, which is directly related to road capacity computer system bus speed and reach of the storage devices. Thus, the criteria for the entire system to a head, and comparatively it and the price. One mali unlikely detail is often forgotten - COMPATIBILITY. 100% compatibility with the DOS operating system or DOS applications, and support for the EGA, CGA and MDA standards and VESA BIOS extensions for higher resolution of 640 480 PCI-Express graphics card is of importance and AGP compatibility. As noted in practice mean? Old accounting applications written for MS-DOS environment will have a 'miserable' image on the monitor if graphics card does not know well 'explain'.

The basic settings on the graphics card can be set are:

Graphics drivers, if they had to be written, for adjusting these parameters. The following Figure shows the different settings of the color compared to the default settings, and describes how to change the color curve.

 Color adjustment  iStripper
Figure* 3.5.19 Adjust color of image.  

To display the image looks everything was aligned, must be entered into the operating system rolled settings for the monitor, which came along with his driver. Picturesque change in the color spectrum resulting from these changes are shown in the left picture box with colors. It is best when the color curve linear. But there are situations when the view is not good, especially when it comes to games, when their graphic image generator gives darker images because it suited for a particular type of graphics card, such as for video game consoles circuits. Then this correction helps, especially 'gamma' correction. Applications for image processing, viewing DVD recordings and the like usually have their corrections that operate within the 'window' apps do not change system settings in general. Good software for image processing has the ability to curve the color printer and adjust the monitor so that the image put out exactly as seen in the photo imaging. Of course, the operating system must be rolled to enter the settings for the printer. So for quality and compliance monitoring system image must have a valid drivers graphics card, monitor, and printer.

An important parameter is the refresh rate of the monitor image ranging from 50 Hz up to 200 Hz, depending on your resolution image display on the monitor. This is the number of images to be displayed in the unit of time on the monitor. Television has a 225 images, one image is repeated twice because the dynamic changes have not been so quick. Although it does not register some flicker of 50 Hz, registers ga human brain, leading to headaches and fatigue after a long labor, and it is good that this frequency is at least 75 Hz. And in this regard should adjust the monitor with the graphics card, because the monitor is that you are looking at the entire day on which the 'lost eyes'. That the monitor should be slightly more powerful features of the graphics card. Due to the enormous extra menu of modern computer programs that useful work space applications to a significant extent reduce, good to have diagonal CRT monitor 19" or more or diagonal LCD monitor 21" or more, which will of course meet the graphics card in terms of labor-resolution images.

As the PC is increasingly focused on the media and how they are processed, unless the growth of software for this purpose, the manufacturers of graphics cards are added new features, such firmware decoding MPEG2 and MPEG4 content and all format DTV/HDTV decoding regarding efficient DVB content and presentation Index coded for the Home Theater. Regarding support for HDMI (High-Definition Multimedia Interface) graphics card has to know forward and audio content to send video and audio content, such as TV set. If installing a complete software for audio support from manufacturers of audio card (or built-in chip on the motherboard) is not necessary complement graphics drivers with audio facilities that come with the software for graphics cards. HDMI is becoming increasingly widespread standard for multimedia applications.


Citing of this page:
Radic, Drago. " IT - Informatics Alphabet " Split-Croatia.
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