A graphics card is essentially composed of a GPU (Graphic Processing Unit) and memory.
The graphics card alone can be considered as a small PC dedicated to graphics applications, independent of the rest of the PC, the only links being the information transferrred through the port and power cable.
Choosing a card is made accordingly to your needs and also your budget:
- For desktop applications, an integrated chip or a low-end graphics card.
- For multimedia applications, a graphics card that can play the desired video format is imperative;
- For 3D video games, a more powerful graphics card will be required;
- For professional (3D graphics) a professional graphic cardis essential.
Structure of a graphics card
The key component that will determine the performance graphics card is the GPU:
A modern GPU is based on different computing units:
- Stream processors (SP:Stream Processors), performing the majority of the calculations on the pixels,
- Texturing units (Texturing Units, TU), responsible for image textures,
- Raster Units (ROPs), responsible mainly for anti-aliasing.
- The most important are stream processors: the higher the number of stream processors is important, the GPU will be more powerful (for a given architecture).
- The trade reference of the graphic card is linked to the GPU.
- To enable the GPU to store its calculations, there is the memory:
- 512 MB is sufficient for graphics input for low end computing.
- 1GB are available for mid-range, and essential for the high end requirements;
In general, the more you expect from high resolution and filtering enabled, it takes more memory.
- There are several types of Memory:
- G-DDR2, G-DDR3, G-DDR4 or G-DDR5 the higher the number, the more memory is fast. This standard is of no reference to the RAM used for your PC: you can have a PC uusing DDR2 and a graphics card DDR5.
- The frequency:
- The higher, the card is more powerful.
- Finally, to connect the GPU and memory, there is the memory bus.
- The width of this bus is important: it may be 64, 128, 256, 384 and 512 bits:
- A larger bus provide higher transfer rate between the GPU and memory are fast.
- Note that: If you consider 2 graphics card sporting the same GPU, but one possess a 128 bits memory bus and other boast a 256 bits, the latter will be more powerful.
You want to sort the cards according to their commercial reference, see the article choose graphics card based on its reference
Performance of graphics cards: Video
For playback of different video formats, the complete decoding of the format by the graphics card is the following:
- MPEG-2: all ATI X series 1000 and beyond, all GeForce 7000 series and beyond are able to perform.
- MPEG4/H.264: all ATI HD 2000 series (except HD 2900) and beyond, all GeForce 8000 series (except old 8800) and beyond are able to perform.
- VC-1: all ATI HD 3000 and all GeForce 9000 series (except 9600 GT) are able to perform.
- MPEG-2 is commonly used as format for standard DVD, the MPEG-4/H.264 and VC-1 concern the Microsoft HD DVD and Blue Ray.
Tips before buying graphics card
The equipment offered in the following paragraphs are intended for a new PC:
If you want to change the graphics card on an existing PC, you must pay attention to different compatibility constraints, including size, power and CPU, please read: Upgrade your PC
- Be cautious about the pitfalls realted to memory standards:
- Size: A graphics card with lots of RAM is useless if the GPU is not powerful: for example, it is unnecessary to have a 1GB ATI HD 4670 or HD 5670 or nVidia 9500 GT, a GT 220 or GT240.
- Type: various types of memory are sometimes offered for the same GPU: G-DDR2, G-DDR3 memory and sometimes the G-DDR5. For example for the GT 240, some have the 1700MHz DDR5 (recommended), but others have the 900Mhz G-DDR3.
To be completed.....