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- Generalities


- Small history of the videocards

- The resolution and the number of colors

- The refreshment speed

- Video memory

- Connectors: PCI, AGP...

- Adequacy to the use of the computer

Updated page
10/25/1999


Author:
Juan Herrerías Rey
 

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What is... the videocard?


 

The refreshment speed

The refreshment, apart from the Coca-Cola, is the number of times that draws the screen in second (like the stills of the movies); obviously, major all that is less one will tire the sight to us and we will work more comfortable and with less visual problems.

It measures itself in hertzes (Hz, 1/second), so it means 70 Hz that the screen shows every second 1/70, or 70 times per second. To work comfortably we will need this 70 Hz. To work ergonómicamente, with the minimum of visual fatigue, 75-80 Hz or more. 60 Hz is the absolute minimum; below this number the eyes suffer very much, and a few minutes are enough to begin feeling burning sensation or even a small headache.

Formerly a so called horrible skill was used interlaced, that consists of the fact that the screen shows in two spent ones, first the odd lines and then you give birth to them, therefore 70 interlaced Hz it is equivalent to little more than 35 without interlacing, what tires the sight exceedingly. Fortunately the skill is in desuetude, but in the monitors of 14 " it has been used even does a pair of years.

The motive of so much interlaced and not interlaced is that to construct monitors that support good refreshment speeds to high resolution is quite expensive, therefore the videocard was using these truquitos to save at the cost of the sight of the user. Nevertheless, all the videocards cannot offer any refreshment speed either. This depends on two parameters:

  • The speed of the RAMDAC, the digital analogical converter. It measures itself in MHz, and must be the possible biggest thing, preferably superior to 200 MHz.
  • The speed of the memory of video, preferably of some type advanced like WRAM, SGRAM or SDRAM.

 

Video memory

Since we have said, his size influences the possible ways of video (all that more exists, more options we will have); also, his type determines if we will obtain good speeds of refreshment of screen or not. The most common types are:

  • DRAM: in the most ancient cards, already descatalogadas. Bad characteristics; maximum refreshments I half-close 60 Hz.
  • EDO: or "EDO DRAM". Till not long ago standard in quality cards average - fall. Very variable refreshments depending on the speed of the EDO, between 40 ns the worst and 25 ns the best.
  • VRAM and WRAM: quite good, although in desuetude; in typical quality cards, very good.
  • MDRAM: a type of not very common memory, but of high quality.
  • SDRAM and SGRAM: at present used for the most part, very good services. The SGRAM is SDRAM especially adapted for graphic use, theoretically enclosed a little more rapid.

 

Connectors: PCI, AGP...

The graphic card, like added that it is to the PC, gets connected to this one by means of a slot or groove of expansion. Many types of grooves of expansion have been created precisely to satisfy to the enormous quantity of information that transmits every second to the graphic card.

  • ISA: the original connector of the PC, little adapted for graphic use; as soon as we come to cards with a certain acceleration grade it turns out to be insufficient. Used up to the first VGA "accelerating graphs", those that not only represent the information but they accelerate the speed of the system on having liberated to the microprocessor on behalf of the graphic task by means of diverse optimizations.
  • VESA Local Bus: more than a slot a bus, a connector intimately joined the microprocessor, what increases the data transmission speed. A cheap solution used in many badges 486, of good yield but technologically not very advanced.
  • PCI: the standard for connection of graphic cards (and peripheral multiple others). Sufficiently fast for the current cards, although something I press hard for 3D that approach.
  • AGP: neither a slot, but a port (something like local bus), thought only for graphic cards that there transmit hundreds of MB/s of information, typically them 3D. It presents few profit in services opposite to PCI, but it has the advantage of which the cards AGP can use memory of the system as a video memory (which, nevertheless, penalizes very much the yield).

In any case, the connector can only limit the speed of a card, does not raise it, what he explains that some cards PCI should be much more rapid than other cheaper or worse made AGP.

 

Adequacy to the use of the computer

Obviously, it is not the same to choose a graphic card to be employed at Word in a monitor of 15 " than to do CAD in one of 21 ". One notice that I always allude to the monitor with which they are going to work, because a very good card cannot demonstrate it in a bad monitor, not on the contrary.

The indications are generic; to know more on this topic, go to the videocards paragraph in What components to buy for...

  • Office computerization: cards in format PCI or AGP, with good microprocessors in 2D, without needs 3D specific; capable of 1024x768; with approximately 2 ó 4 MB; and with good refreshments, environment to 70 or 80 Hz. A typical example "of mark" is Matrox G200, or any cradle in the chip i740.
  • Games and CAD in 3D: with special mikes for 3D, with a lot of memory (between 8 and 32 MB), generally of mark and preferably AGP. For example, the cards based in chips TNT2 or Voodoo3.
  • Images and CAD in 2D: with chips of 64 ó 128 bits, memoirs ultrarrápidas, capable of points coming to 1600x1200 to 70 Hz or more, with 4 MB or more. Anyone with a superchip, SGRAM/SDRAM and a 225 MHz RAMDAC or more.

In general, at present the topic takes root in knowing if it is needed or do not support 3D; the acceleration 2D, that is to say, that of Windows, office computerization, Internet, etc, is for a long time more than obtained; almost all the cards give spectacular and almost indistinguishable numbers in any test 2D.

 


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