The Video card or video adapter are one of the main parts of the modern computer since exactly he realizes the conclusion of the scene on screen of the monitor. Exactly contact of the person is realized through monitor with computer. So earlier, when was not an видеоадаптеров and monitor, information was removed on indicators, where not that graphs and text that was not. The First видеоадаптер in IBM compatible computer, was identified he MDA, was monochrome. With development computer developed and video card. Right behind went already colour CGA. Further, company fought for amount colour not only, which could support their card, but also for greatly supporting permit. 3D Boosters appear With beginning of the using 3D graphs. Now fight happened to for quality and velocity of the processing 3D scenes. The Modern video card carries on board following elements:

1. SVGA-kernel;
2. the kernel 2D booster;
3. the kernel of the processing 3D graphs;
4. the video kernel;
5. video BIOS;
6. the controller to memories;
7. the video memory;
8. the interface main buses;
9. the interface of the external port of the entering-conclusion;
10. the converter RAMDAC;

If initial problem of the video cards was shown transformation of the digital signal in video signal with the following conclusion of the scene on monitor (this concern with RAMDAC) then with appearance 3D graphs in composition of the video card became to enter 3D accelerator. On he is entrusted problems on enormous mathematical calculations, connected with processing 3D graphs and проецированием her(it) on plane (the screen of the monitor). The Modern video card has TV in\out that allows to realize the conclusion of the scene on television set. DVI interface allows to connect the digital equipment - a cameras, LCD monitors. Thereby, modern video card executes the enormous amount a function, in which we shall try to understand.

3D graphics

The Spatial computer graphics often is identified three-dimensional or 3D graphics (where D this dimension, measurement ). All subjects around us three-dimensional, but that see on screen of the monitor двухмерное or flat. The Difference, in amount of the coordinates first of all. To exactly know the place of the position of the subject to us necessary three coordinates to remove the scene on screen of the monitor it is enough two. В than sense 3D booster? This is because in the event of with 3D graphics with standpoint of the video card scene is three measured that is to say video card counts three coordinates for conclusion of the scene, but already got picture проецирует on plane. Certainly, projection is got двухмерной, but is reached effect three measurements each subject possible to consider on either side, effect of the prospect etc. All this requires the great computing resource of the video card and CPU. The most interesting begins under текстурировании (раскрашивании) 3D object. Teksturirovanie complex and ресурсоемкий process. But previously than something paint, it is necessary to understand, but that in general to paint that is to say build objects themselves. The Majority 3D exhibits use полигональную technology of the building object. The Building полигональной three-dimensional scene is realized by video card in several stages:

1. The Determination of the condition object initial stage. Here logic further action is formed. For instance if in play your hero kill, that why in general прорисовывать scene.
2. Models are formed On втором stage for all object. For instance, object one (the crock), but models different in accordance with condition reaped, kill, was transformed.
3. In полигональной of technologies each object consists of the most simplest planes (the triangle), named firing range. On the one third stage buildings model is split on firing ranges.
4. Here is, finally, and текстурирование, preliminary. The most Most important stage of the building. At this stage for each firing range is defined, what exactly texture and what exactly way (by means of what algorithm) will be on it is assessed. Since текстурирование preliminary all calculations usually produce for tops triangle.
5. The Determination of the position of the camera. Coming from result, are defined coordinates of the tops firing range, distance from plane of the projections before tops, corners of the review.
6. The Determination and cutting off unencountered object or their part. The Slider of the program and video card must as possible more exactly execute this function, in order to avoid error. Really little pleasantly if before you прорисовывается the object residing behind, or on border of the review suddenly disappears the whole crock though for limit of the review is found only his(its) part. Information on degree of the removing object fits in Z-buffer.
7. The Stage of the installation primitive. At this stage given about coordinate of the tops, assigned to texture, parameter to luminosity and others happen to to целочисленному type suitable to processing by equipment.
8. Penultimate (in some cases last) by stage is рендеринг. Occurs the building an двухмерной to projections three-dimensional scene in buffer of the frame. Citing to information in Z-buffer, попиксельно are painted all visible objects.
9. Not obligatory, but often used stage of the final processing. What or filter or effect is used to ready scene.

Above broughted stages in miscellaneous product can be executed differently. Their can change the places, some can be executed not one-shot, but sense beside they remain one. Depending on video card part operation can miscalculate software, a part hardware. The Protozoa видеоадаптеры hardware execute last two functions. The Modern cards, carrying on board special graphic processor, capable to count the stages of the transformation, calculations of the illumination, imposition of the textures. Logistical that than more operation video card produces hardware, that less loads up CPU, and that мощнее must be she itself. Also logistical that than more slider of the program conducts the firing range for making object, that real they look.

The Main task computer graphs force drawn to look real. But not one computer play (there is in view of modern home computer) did not reach today photo - an реалистического level graphs. The Deal in texture and not only in them. Than above permit of the texture that more видеопамяти is required for her(its) keeping. Than more firing range, that above must be a velocity of the graphic processor for their processing and potting. Exists the Empirical rule, according to which 10000 firing ranges give the acceptable quality graphs, 50 000 quality close to home video, allow to approach to фотореализму only over 100 000 firing ranges. For present-day day best plays have at the average 15 000 20 000 firing ranges in scene (the most complex 40 000 in separate scene), but quality graphs increases to account of the filtering. Filtering so allows to unload видеопроцессор distant, but consequently weakly visible objects are flooded by texture of the smaller permit and детализации (MIP mapping).

Hardware processing 3D graphs

The Whole composition of the video card possible conditionally to divide into several blocks. Main brain centre of the video card, concerning with main calculation, building and projection geometric processor. The Block of the illumination concerns with the light. That shines, whence shines, where shines. Where shines main question since for each firing range it is necessary to count the degree to luminosity. Particularly sharply, the question cost(stand)s about amount of the sources of the light. Such features no nor in one прайсе though factor rather interesting. We shall Take the third generation of the video cards GeForce 256 from nVidia was calculated on two sources of the light, and beautifully with they worked, but cost to appear third or fourth source as velocity sharply fell, began the brake. Little who knows that Radeon 256 from ATI hardware supports the dynamic calculation before 8 sources. The Ithaca, having illuminated firing ranges it is necessary to define, what firing range will is seen, but what no (for instance, one object barriers other). This concern with the block of the processing the buffer of the frame. Defines he this on the contents Z-buffer, where for top of each firing range is kept Z-coordinate (the degree to remotenesses). The Visible pixels are processed in block of the textures. The Processed pixel fits in buffer of the frame, changing or mingling with old (the combination, transparency etc.).

For speedup of the processing the textures use parallel work several blocks conveyor. If there are 2-3 conveyors then for one cycle possible to process 2-3 textures sootvetstvenno. Before directly conclusion on monitor, picture is processed algorithm special effect, for instance, imposition of the mist and all-out smoothing.

In general, picture is powerfully said. The Picture this that see on screen of the monitor. To from all above described processes to get the picture, it is necessary to convert the digital signal in video. Than and concerns with RAMDAC (Random Access Memory Digital Analog Converter) i.e. numeral/analog converter.

Company	Name	Frequency RAMDAC, MHZ
nVidia	GeForce	350
nVidia	GeForce2 GTS	350
nVidia	GeForce3/4	350
nVidia	GeForce FX	400
ATI	Radeon 8500	350
ATI	Radeon 9700	400

The Main feature RAMDAC are vertical unrolling and greatly supported permit. One of first RAMDAC was designed IBM in 1985г. and had a permit 320х200 at цветовом range 8 bit. Today standard is considered RAMDAC over 1600х1200, 32 bit, unrolling - 75-85 Hz. Obligatory became support Direct color (the direct access to DAC for independent adjustment each of three primary colors), function has got the name a gamma - a correction. 32 bit this 8 bit on colour that around 16,7млн. colour, to account gamma - a correction range enlarges.

Usually is not flaunted (but зачастую is cushioned by producer) factor Slew Rate. This time, during which ray of the gun of the picture tube is included, reaches maximum brightness, and goes out. Happens so that at radio frequency of the renovation ray, not haved time to to, begins прорисовывать following pixel. It Is Got that new pixel already blazes, but old not yet redeem. Thence замыливание i.e. oiling of the colour on nearby pixels.

It is Necessary to say that frequency RAMDAC and frequency of the unrolling miscellaneous belongings. For instance: 1280х1024х75Гц = 98,3 Mhz it is Necessary to take into account time for cut-in/switching off the pulse and flyback of the ray, on this result follows to multiply by 1,5: 98,3 x 1,5 = 147,45 Some video card and their frequencies RAMDAC:

Permit under 85 Hz	Neobhodimaya passband of the monitor, MHZ	Neobhodimaya frequency RAMDAC, MHZ
1920x1600	395	400
1600x1280	265	270
1600x1200	245	250
1200x1024	160	170
1024x768	110	150
800x600	110	150
640x480	110	150

If necessary to select the video card for concrete monitor, necessary to match the frequency RAMDAC with passband of the monitor since in the event of discrepancy possible leaving the monitor from building. Today video card has digital and analog entry/output for connection external device. Analog output is most often used for viewing film on television set since he has greater, than monitor диагональ. For connection digital device, for instance, digital camera, is used DVI interface. Thereby, big importance is spared quality 2D graphs. However her(its) processing does not require the greater resource, but since connection above mentionned device is bound, basically, with transformation of the digital signal in analog conversely, that quality mainly depends on RAMDAC.

Particularities видеопамяти

The Textures of the high permit have a greater sizes. So capacity of the video card not in the last queue depends on features of the video memory. The First chip to memories suitable to use in computer graph were DRAM, which had an anisochronous access (worked at independent frequency). Cost(stand)s to say that for sensing of information was needed two cycles. Today, the producer miscellaneous use the different types to video memory.

1. VRAM (video RAM). It Was Developed as alternative DRAM, is called to enlarge capacity to account record and sensing to information for one cycle. The Variant WRAM (windows RAM) has best, approximately, on 25% reception capacity, has a row built-in, often used function. Because of special access method, is used only producer Matrox and Number Nine.
2. 3D-RAM. The Designed company Mitsubishi. Unites all best from architectures VRAM, WRAM and DRAM. Is it Specially optimized for visualization 3D graphs. Has limited application, in connection with high cost.
3. CDRAM (Cached RAM). Includes the usual block to memories DRAM + block cache type. It Is Used as текстурной to memories in professional видеоконтроллерах. The Send rate = 800 Mb/sec.
4. MDRAM (Multi bank DRAM). The Designed company MoSys. It Is Characterized presence ensemble independent banks to memories.
5. SGRAM (Synchronous Graphics RAM). Is a variant DRAM. A synchronous access has Unlike DRAM.
6. Direct RAM Bus DRAM. Differs the own internal bus (RAM Bus channel), send rate given on which aproximately is 800 Mb/sec. Theoretically peak reception capacity DR DRAM = 3,6 Gb/sec, on bus 64 bit under 100 Mhz.

DDR SDRAM (Double Data Rate SDRAM). Probably the most wide-spread видеопамять today. This is bound both with technical feature, and with the prices on memory given architectures. The Maximum passband reaches 3,2 Gb/sec at frequency of the system bus 166 Mhz.

Capacity

In the first place 3D boosters is accepted value on capacity, but only on quality of the picture then. Obviously that factor to velocities, basically, is defining at choice of one or another card. The Modern video card for home computer is calculated, basically, on work with 3D play. So, dialect about capacity, usually сосредотачиваются on two parameters Fill rate (time of the potting 3D models) and Throughput (the velocity of the building 3D models). The Producers, in turn, indicate peak capacity, which noticeably differs from factors of the testing on concrete exhibits. Real importances Fill rate at the average below peak on 20%, but Throughput from 27% before 67%. Importances above specified factors in многом hang from exhibits, on which were tested cards since in different exhibits can be used different methods текстурирования and filtering. For instance, the most popular on today видеопамять DDR SDRAM reaches peak reception capacity when processing united array only, when processing separate element capacity falls. The Factor Fill rate basically depends exactly from видеопамяти and graphic processor since exactly between they occur the basal metabolism given under текстурировании. In building models themselves very important role plays CPU and operative memory of the computer. Thence such scatter of importances of the factor Throughput and dependency to capacity of the video card from CPU. The most evident this dependency was beside cards first and the second generation (except Voodoo). The Third generation already had its geometric processor, and dependency decreased (but did not disappear). The Fourth generation for full выкладки newly requires the powerful central processor since in exhibits with complex graphics on he is entrusted calculations of the physical processes at building of the scenes. Identical for Radeon 9700 and GeForce Fx follows to consider the processors on 2,5 GGC and more. The more quick processors do not cope with entrusted duty and hold up the system as a whole. From above described parameter depends the amount of the personnel(frames) at second (fps) main demonstrative factor. Not enterring into details on him possible graphically to say, holds up the video card or no.

Review some видеокарт and their user estimation

Not secret that at choice of one or another video card for user solving importance has exactly power, but for that функциональность only. The correlation price/velocity/quality is Got. Studied some features, having peeked in прайсы and comparable these three factors, each itself can solve what video card to him today выгоднее to gain. It is Necessary to say that on today about each models more-more objective opinion formed beside users:

1. NVidia GeForce256 (the different modifications). Has much goodness 2D graphs. The Quality 3D without remarks. The Velocity on modern yardstick insufficient. Realizes all their own possibility only in completing with DDR SDRAM. However even under low prices correlation price/quality unbeneficial.
2. NVidia GeForce2 GTS, ATI Radeon 256 (the different modifications). The High quality of the scene both in 2D and 3D exhibits. Noticeably increased capacity when work with 3D graphics. Because of insufficient reception capacity видеопамяти holds up on high permits under 32bit colour. It Is Recommended at lack of the facilities on more modern model.
3. NVidia GeForce3, ATI Radeon 8500. Have several modifications. Insufficient reception capacity to video memory in not small degree is compensated by methods of the work with her. As effect increased capacity in 3D exhibits. The Acceptable prices on younger modifications allow to recommend the card data for computer of the average class.
4. NVidia GeForce4, ATI Radeon 9000. The Line GeForce has a subgroups senior Titanium and younger with index MX. On correlation price/quality leader Titanium 4200 (the price on models senior not proportional quality, but MX powerfully pared in possibility). Radeon on втором place. MX possible to recommend for cheap computer

NVidia GeForceFX, ATI Radeon 9700. Support the most latest methods of the work with 3D graphics. Ahead of all on velocities, the quality and as effect on the price. The fan of the plays is Recommended.

Author: А. V. Savin It Is Added: 30.04.2007