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Buying Guide to Graphics Cards
The graphics card is a vital performance component of your computer, particularly if
you play 3D games, or work with graphics and video content. The graphics card sits in
an expansion card slot in your PC and it is specifically designed to process image data
and output it to your monitor, enabling you to see it. A graphics card works by
calculating how images appear, particularly 3D images, and renders them to the screen.
3D images and video images take a lot of processing capacity, and many graphics
processors are complex, require fans to cool them and need direct power supply. The
graphics card consists of a graphics processor, a memory chip for graphics operations,
and a RAMDAC for display output. It may also include video capture, TV output and SLI
and other functions.
Graphics Cards
What are your needs?
The first decision you need to make is whether you need a graphics card for handling
3D images or whether you are simply requiring 2D image rendering. For 2D
requirements, you need only a low-cost solution. In many cases, an integrated graphics
solution will suffice for 2D applications.
However with 3D graphics, the performance of the graphics card will impact directly on
the frame rate and image quality of 3D programs and games. The differences between
the low and high-end cards can be substantial, both in cost and performance.
Rendering 3D graphics is like lighting a stage, both the geometry of the shapes in
question and the lighting of it need to be taken into account. The geometry of an image
calculates the parts of an object that can and can't be seen, the position of the eye and
its perspective. The lighting is a calculation of the direction of the light sources, their
intensities and the respective shadows that occur. The second part to presenting a 3D
image is the rendering of colours and textures to the surfaces of the objects, and
modifying them according to light and other factors.
Most modern graphics cards include a small microchip called the Graphics Processing
Unit (GPU), which are provide the algorithms and memory to process complex images.
They reduce the workload of the main CPU, and provide faster processing. Different
graphics cards have different capabilities in terms of processing power. They can
render and refresh images up to 60 or more times per second, calculate shadows
quickly, create image depth by rendering distant objects at low resolution, modify
surface textures fluidly and eliminate pixelation.
What Specifications to Consider
Processor clock speed
This impacts on the rendering capability of the GRU. The clock speed itself is not the
critical factor. Rather it is the per-clock performance of the graphics processor, which is
indicated by the number of pixels it can process per clock cycle.
Memory size
This is the memory capacity that is used exclusively for graphics operations, and can be
as much as 512MB. The more demanding your graphics applications are, the better you
will be served with more memory on your graphics card.
16-32M
64M
128M
256M
512M
640M and more
Memory bandwidth
One thing that can slow down 3D graphics performance is the speed at which the
computer delivers information to the graphics processor. A higher bandwidth means a
faster data transfer, resulting in faster rendering speeds.
Shader model
DirectX Shader Models allows developers control over the appearance of an image as it
is rendered on screen, introducing visual effects like multi-layered shadows, reflection
and fog.
Fill rate
This is the speed at an image can be rendered or "painted". This rate is specified in
texels per second, the number of 3D pixels that can be painted per second. A texel is a
pixel with depth (3D). The fill rate comes from the combined performance of the clock
speed of the processor and the number of pixels it can process per clock cycle, and will
tell you how quickly an image can be fully rendered on screen.
Vertices/triangles
Graphics chips don't work on curves, rather they process flat surfaces. A curve is
created by multiple flat planes arranged to look like a curve. 3D objects are created with
multiple triangular surfaces, sometimes hundreds or even thousands, tessellated to
represent the curves and angles of the real world. 3D artists are concerned with the
number of polygons required to form a shape. There are two different types of
specification: vertices per second (I.e., angles the triangles), and triangles per second.
To compare one measure with the other, you have to take into account the fact that
adjacent triangles share vertices.
Anti-aliasing
A technique used to smooth images by reducing the jagged stepping effect caused by
diagonal lines and square pixels. Different levels of anti-aliasing have different effects
on performance.
RAMDAC
The Random Access Memory Digital to Analogue Converter takes the image data and
converts it to a format that your screen can use. A faster RAMDAC means that the
graphics card can support higher output resolutions. Some cards have multiple
RAMDACs allowing that card to support multiple displays.
TV-out
Some graphics cards provide the option to connect a television via either a composite
(RCA) or S-Video connector. TV Out
S-video Out
S-video In and S-video Out (VIVO)
YPbPr Connection for HDTV
DVI
Some graphics cards include a connector for DVI monitors, handy because a lot of LCD
screens support DVI. DVI offers better image quality than the standard VGA connector.
Dual-head
Dual-head is a term used when two monitors are used side by side, stretching your
desktop across both.
SLI (Scalable Link Interface.)
With SLI you can couple two graphics cards in your computer, enabling each card to
take half the rendering thereby doubling the performance.
When considering your graphics card, it pays to think about how much you need your
computer to process your graphics output. Using a high end graphics card with a high
pixels per clock rating, large memory, fast processor and other features means that you
can run the latest games efficiently, or work in intensive graphics development.
Different Models
While there are many vendors of graphics cards, there are actually only two major
manufacturers of chips for graphics cards. Nearly every graphics card on the market
features a chip manufactured by either ATI or Nvidia. Cards using the same graphics
chip will perform roughly the same as each other. However, even though they use the
same chip, some feature slightly higher clock speeds, as well as manufacturer
guaranteed overclocking-an even higher clock speed than that specified. Other factors
that will influence your decision should include the amount of memory a card has
(128MB, 256MB, 512MB) and its additional features, such as TV-Out and dual-screen
support.
The graphics card is a vital performance component of your computer, particularly if
you play 3D games, or work with graphics and video content. The graphics card sits in
an expansion card slot in your PC and it is specifically designed to process image data
and output it to your monitor, enabling you to see it. A graphics card works by
calculating how images appear, particularly 3D images, and renders them to the screen.
3D images and video images take a lot of processing capacity, and many graphics
processors are complex, require fans to cool them and need direct power supply. The
graphics card consists of a graphics processor, a memory chip for graphics operations,
and a RAMDAC for display output. It may also include video capture, TV output and SLI
and other functions.
Graphics Cards
What are your needs?
The first decision you need to make is whether you need a graphics card for handling
3D images or whether you are simply requiring 2D image rendering. For 2D
requirements, you need only a low-cost solution. In many cases, an integrated graphics
solution will suffice for 2D applications.
However with 3D graphics, the performance of the graphics card will impact directly on
the frame rate and image quality of 3D programs and games. The differences between
the low and high-end cards can be substantial, both in cost and performance.
Rendering 3D graphics is like lighting a stage, both the geometry of the shapes in
question and the lighting of it need to be taken into account. The geometry of an image
calculates the parts of an object that can and can't be seen, the position of the eye and
its perspective. The lighting is a calculation of the direction of the light sources, their
intensities and the respective shadows that occur. The second part to presenting a 3D
image is the rendering of colours and textures to the surfaces of the objects, and
modifying them according to light and other factors.
Most modern graphics cards include a small microchip called the Graphics Processing
Unit (GPU), which are provide the algorithms and memory to process complex images.
They reduce the workload of the main CPU, and provide faster processing. Different
graphics cards have different capabilities in terms of processing power. They can
render and refresh images up to 60 or more times per second, calculate shadows
quickly, create image depth by rendering distant objects at low resolution, modify
surface textures fluidly and eliminate pixelation.
What Specifications to Consider
Processor clock speed
This impacts on the rendering capability of the GRU. The clock speed itself is not the
critical factor. Rather it is the per-clock performance of the graphics processor, which is
indicated by the number of pixels it can process per clock cycle.
Memory size
This is the memory capacity that is used exclusively for graphics operations, and can be
as much as 512MB. The more demanding your graphics applications are, the better you
will be served with more memory on your graphics card.
16-32M
64M
128M
256M
512M
640M and more
Memory bandwidth
One thing that can slow down 3D graphics performance is the speed at which the
computer delivers information to the graphics processor. A higher bandwidth means a
faster data transfer, resulting in faster rendering speeds.
Shader model
DirectX Shader Models allows developers control over the appearance of an image as it
is rendered on screen, introducing visual effects like multi-layered shadows, reflection
and fog.
Fill rate
This is the speed at an image can be rendered or "painted". This rate is specified in
texels per second, the number of 3D pixels that can be painted per second. A texel is a
pixel with depth (3D). The fill rate comes from the combined performance of the clock
speed of the processor and the number of pixels it can process per clock cycle, and will
tell you how quickly an image can be fully rendered on screen.
Vertices/triangles
Graphics chips don't work on curves, rather they process flat surfaces. A curve is
created by multiple flat planes arranged to look like a curve. 3D objects are created with
multiple triangular surfaces, sometimes hundreds or even thousands, tessellated to
represent the curves and angles of the real world. 3D artists are concerned with the
number of polygons required to form a shape. There are two different types of
specification: vertices per second (I.e., angles the triangles), and triangles per second.
To compare one measure with the other, you have to take into account the fact that
adjacent triangles share vertices.
Anti-aliasing
A technique used to smooth images by reducing the jagged stepping effect caused by
diagonal lines and square pixels. Different levels of anti-aliasing have different effects
on performance.
RAMDAC
The Random Access Memory Digital to Analogue Converter takes the image data and
converts it to a format that your screen can use. A faster RAMDAC means that the
graphics card can support higher output resolutions. Some cards have multiple
RAMDACs allowing that card to support multiple displays.
TV-out
Some graphics cards provide the option to connect a television via either a composite
(RCA) or S-Video connector. TV Out
S-video Out
S-video In and S-video Out (VIVO)
YPbPr Connection for HDTV
DVI
Some graphics cards include a connector for DVI monitors, handy because a lot of LCD
screens support DVI. DVI offers better image quality than the standard VGA connector.
Dual-head
Dual-head is a term used when two monitors are used side by side, stretching your
desktop across both.
SLI (Scalable Link Interface.)
With SLI you can couple two graphics cards in your computer, enabling each card to
take half the rendering thereby doubling the performance.
When considering your graphics card, it pays to think about how much you need your
computer to process your graphics output. Using a high end graphics card with a high
pixels per clock rating, large memory, fast processor and other features means that you
can run the latest games efficiently, or work in intensive graphics development.
Different Models
While there are many vendors of graphics cards, there are actually only two major
manufacturers of chips for graphics cards. Nearly every graphics card on the market
features a chip manufactured by either ATI or Nvidia. Cards using the same graphics
chip will perform roughly the same as each other. However, even though they use the
same chip, some feature slightly higher clock speeds, as well as manufacturer
guaranteed overclocking-an even higher clock speed than that specified. Other factors
that will influence your decision should include the amount of memory a card has
(128MB, 256MB, 512MB) and its additional features, such as TV-Out and dual-screen
support.