Understanding Graphics Cards

Table of contents:

  • 1.Understanding Graphics cards: what they do
  • 2.Components of a graphics card
  • 3.Full scene anti aliasing (FSAA) and Anisotropic filtering (AF)
  • 4.Monitor connections
  • 5.PCIe{express) connection to the motherboard
  • 6.Understanding frame rate per second
  • 7.SLI and CrossfireX

1.Understanding Graphics cards: what they do

The job of a graphics card is to process and build the images that end up on your computer monitor.

Computers will for the most part come with graphics  either integrated on the motherboard or within the processor. This is fine for everyday tasks such as checking email surfing and the occasional Youtube video.

However for those who use there computer for high powered gaming this kind of setup will not be enough. Therefore the use of a dedicated graphics unit is necessary to deal with the demanding nature of gaming. Having a graphics card which is solely dedicated to the graphical side of computing  means that the computer can deal with the most demanding of games without becoming bottle necked or overloaded by the amount of processing it is required to do.

The graphics card on its own deals with the graphics leaving the CPU on the motherboard to process everything else. This divide in duties is why gaming computers can run as smoothly as they do while under such a heavy work load.

 

2.Components of a graphics card

When you look at a graphics card you will notice that it is rather similar to the motherboard, but on a smaller scale

Like the main motherboard the Graphics card has its own processor which deals with the processing of data into images.

The graphics card processor can often be even more complex than the main CPU on the motherboard. This is because graphical processing and building the images needed for the monitor is a complicated procedure.

All of the most modern and high end graphics card now come with a fan or heat sink that sits on top of the processor. This is because the  heat produced while it is processing can be very high, due to the incredible amount of calculations it runs through whilst a game is being played.

It also has, like the motherboard its own dedicated RAM, this is used to store the images produced by the processor so they can then be sent out in sequence.

 

3.Full scene anti aliasing (FSAA) and Anisotropic filtering (AF)

Very much like the motherboard CPU which has features like turbo boost,  the graphics card processor has its own box of tricks. These come in the form of full scene anti aliasing and anisotropic filtering these are explained below:

Full Scene anti aliasing (FSAA):

This is a trick used by the graphics card processor in order to smooth the edges of images. If you look at old games of the past running on basic graphics cards you will notice on the edge of objects especially slanted lines there is whats called a step ladder of pixels rather than a smooth line. Look at the example below to see the anti-aliasing effect.

 

Anisotropic filtering:

Anisotropic filtering is also important when it comes to understanding graphics cards. It is another trick used to not only increase quality but to save on performance, allowing for a smoother playing experience.

Look at the picture below to see the effect of Anisotropic filtering:

 As you can see from the image on the right it is of higher quality than the one on the left.

The reason anisotropic filtering came about was because graphics cards use a thing called Tri-linear filtering. This lowers the quality of the image as it disappears into the distance. This is to important as it allows the graphics card to run more smoothly as mapping the whole image at the highest quality would not be efficient. The problem with this technique was that the changes in quality as the image gets more distant was very obvious and gave the image too much of a blurred look. Anisotropic filtering counteracts this by smoothing the transition points in the mip map.

for more detail check out: http://en.wikipedia.org/wiki/Anisotropic_filtering

 

5.Monitor connections

The monitor connection is the output from the graphics card to  the monitor. Because there are more than one type of monitor most graphics cards have at least 2 different outputs.

The DVI output supports the more modern LCD screens where as the VGA supports the CRT format monitors.

                                           DVI:                                                                        VGA

      

 

As LCD monitors are now the modern standard for gaming monitors a lot of new graphics cards will have 2 DVI outputs, and not even bother with a VGA output.

However you can still buy a DVI to VGA adapters if you still prefer to game using a CRT monitor.

For more detail on DVI outputs: http://en.wikipedia.org/wiki/Digital_Visual_Interface

 

6.PCIe{express) connection to the motherboard

If you look at the graphics card above and look at the strip that the arrow is pointing too, this is where it connects or slots into the motherboard.

Most modern graphics cards use the PCI express x16 slot on the motherboard.

PCIe replaced PCI and PCIx slots as the preferred method of data transfer between the graphics card and the motherboard. Originally the PCI slot was used for all dedicated cards such as graphics, sound and network cards. The Problem with the PCI slot was that although it provided a reliable method of data transfer it became too slow. This was most notable with graphics cards, which became ever more powerful and demanding in terms of data used and transferred. This led to improvements such as the PCIx connection. However it wasn’t until the PCI express connection that graphics cards had a connection which was fast enough for there ever evolving needs.

The PCI express x16 which is now the standard connection used by graphics cards is capable of packet data transfer of up to 6.4GB in both direction.

7.Understanding frame rate per second

frame rate is the measurement of frames per second. This is often one of the most talked about things discussed by graphics card enthusiasts. The higher the frame rate the smoother the game play. The human eye can usually see up to 25 frames per second. Modern games, however, use about 60 frames per second in order to play smoothly.

The main test of frame rates is to measure them when playing a very demanding part of a game. For example if you are playing a first person shooter such as battlefield 3, you would test it when there is a part of the game with explosions and gunfire.

Modern graphics cards are designed to be able to handle even the most challenging of games. Of course it also depends on the speed of the rest of your computer. Your main CPU will play a big part in performance.

8.SLI and CrossfireX

SLI and Crossfire are essentially the same thing but made by different companies. SLI is the invention of NVidia where as Crossfire is the invention of AMD for their Radeon cards. Here is a break down of how both work and what they do.

 

NVidia SLI

It

Scalable Link Interface (SLI) is the invention of NVidia. This is to facilitate the use of more than one graphics card side by side in one computer.  This was an idea that first came into use around 2004. However it has advanced considerably since then.

It requires two graphics cards to be plugged into two PCI express slots side by side on the motherboard in a slave master configuration.

When two graphics card are running side by side they can then share the work load that one graphics card would usually deal with. This method works best when two identical model graphics cards are used.

There are a few different methods used by the SLI technique to split the work load between the two graphics cards:

Alternate Frame Rendering (AFR)

This method utilizes both graphics cards by giving each each graphic card a frame to process in sequence. For instance graphics card one will deal with frames: 1,3,5,7,9 etc, and graphics card two will deal with frames: 2,4,6,8,10.

There are some issues with this technique mainly due to input latency and bottle necking.

Split Frame Rendering (SFR)

This is a much more common technique where the image is literally split in half so one graphics card works on one half of the picture and the second graphics card works on the other half. The screen is not always split  in the same place. This is because certain areas of the screen might have more graphics than others, so each image is divided as equally graphically as possible.

SLI Antialiasing.

We touched on anti aliasing earlier in the articles so you know what it does. In an SLI format the anti aliasing can be increased further as one graphics card can off set the image to one side slightly and the other graphic card goes the other way. This increases the effect of the anti aliasing and therefore increases image quality.

for more detail on SLI check out:  http://en.wikipedia.org/wiki/Scalable_Link_Interface

 

 AMD CrossfireX

 

AMD crossfireX uses many of the same techniques as SLI to split the workload, although in recent years starting with the hd 3000 series there is no longer a master slave configuration and later a single ribbon connecting up both cards. AMD has the capacity to use up to four card together.

Advantages over NVidia’s SLI is that from the HD 3800 series onward you can use cards that are not of the exact model number and still achieve the crossfireX technique.

 

We hope this page has helped you with understanding graphics cards. We will look to add further information whenever we get the chance.

 

 

 

 

Picture acknowledgment:

MD from nl [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

http://commons.wikimedia.org/wiki/File%3AAnisotropic_filtering_en.png

By Bela Nemeth, dipl.ing. (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

By Hyins (Own work) [Public domain], via Wikimedia Commons

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