Buying A Graphics Card: Defining PCI-E, AGP, GPU, RAMDAC, And Other Jargon

Buying A Graphics Card: Defining PCI-E, AGP, GPU, RAMDAC, And Other Jargon
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When looking for a graphics card, if you go into any component store or visit any retailer’s website, it’s likely their description will feature heavily on jargon, abbreviations and acronyms. For the average customer, buying a graphics card can be daunting as a result as many average customers will likely be baffled by their meaning. So, what does the jargon, abbreviations and acronyms actually mean in plain terms?

Most people will find that the abbreviations reflect both the card’s actual Hardware and also the cards' architecture. This article will feature on the terms used to describe a graphics card’s hardware setup, with the most commonly encountered terms being:


AGP stands for Accelerated Graphics Port and is an interface used in older graphics cards to connect to an AGP slot on your computer’s motherboard. AGP is becoming less common now, being replaced by PCI-E. If your computer is relatively new, it’s likely to feature PCI-E.


PCI-E stands for Peripheral Component Interconnect Express, and like AGP is an interface used in newer graphics cards to connect to a PCI-E slot on your computer’s motherboard. PCI-E is faster than AGP, allowing for quicker transfer of data to be delivered to the graphics card. The current PCI-E standard is PCI-E 2.0 but graphics cards built on PCI-E technology are typically backward compatible with the older PCI-E 1.0 architecture.

Depending on the type of motherboard you have, you’ll need either an AGP graphics card or a PCI-E graphics card. The technologies aren’t compatible with one another, although some motherboards are available which allow the use of both separately, although only one can be used at a time. That said, you can’t use an AGP graphics card in a PCI-E slot, and vice versa. Most of today’s graphics cards also need to draw power from your computer’s power supply, as depending on the type of card you go for, neither the AGP or PCI-E slot may be able to consistently supply the necessary power to operate the graphics card.

Older computer systems, laptops and many budget systems use integrated graphics chips which form part of the motherboard. These integrated graphics chips perform much slower than dedicated graphics cards and are of little use for games.


GPU stands for Graphics Processing Unit and is the muscle behind your graphics card. This is where all the processing on the graphics card takes place. There are 2 main parts: the microprocessor and the pipelines. The microprocessor performs the complex calculations required for graphic rendering, whereas the pipelines are what converts the 3D image data into 2D display pixels. Microprocessor speeds typically range from 400MHz to 1200MHz, and the higher the frequency, the faster the card is when it comes to calculations. Similarly, the more pipelines a GPU possesses, the faster it can render the images on the display.

Video Memory

Sometimes referred as VRAM, graphics cards have their own dedicated RAM, similar to the memory used by your computer. Today’s graphics card range from a minimum of 128MB to 1GB of video memory, and is typically displayed in descriptions as GDDR followed by a number. The higher the number, the faster the RAM used by the card. Slower, less powerful graphics cards use GDDR2, while the faster cards use GDDR4 currently.

Older computer systems, laptops and many budget systems which use integrated graphics chips on the motherboard typically use system RAM, rather than possessing any dedicated RAM of their own, and can have an adverse impact on the computer’s processing power.


RAMDAC stands for Read Access Memory Digital to Analog Converter. It’s main purpose is to take the digital information received from the GPU and translate it to analog for CRT monitors. However, as more and more LCD monitors are now in use and can display digital signals, RAMDAC is slowly disappearing.

Depending on the speed of the RAMDAC, the converter will be able to support different computer display refresh rates. Refresh rates are inherent to CRT displays, and it is best to work with a refresh rate of over 75Hz in order to minimise screen flicker, which can lead to headache and eye-strain. Essentially, the faster the RAMDAC, the higher the refresh rate which can be used.


The outputs of a graphics card tell the user which display devices can be connected to their card. The most common is the HD-15 connector, which has been an industry standard for some time. The HD-15 connector (also known as a D-Sub connector) consists of a 15-pin connection and is typically represented by a blue block connector. The D-Sub connector is common on CRT monitors and projectors, as well as older LCD displays.

More recently, S-Video has been added so that the graphics card could connect to TVs, DVD players and video recorders. This can also be referred to as VIVO (Video In, Video Out).

Nowadays, all graphics cards are fitted with DVI connectors, known as Digital Video Interface, which allows the use of more up-to-date LCD monitors and delivers better image quality than the HD-15 connector.

Many of today’s graphics card will come with connectors for both HD-15 and DVI, meaning users can use either or both together in order to display signals to two separate monitors. However, more recently, graphics card makers have elected to use two DVI connectors instead of a HD-15 connector, due to the fact that CRT monitors are becoming scarce. Users of CRT monitors don’t need to worry just yet, though, as card manufacturers often include a DVI converter to allow the continued use of CRT displays.

SLI & Crossfire

Both SLI and Crossfire allow the use of two graphics cards in a single system, greatly improving graphics perfomance. However, to use either SLI or Crossfire, your motherboard needs to support the technology and provide a slot for each graphics card. Neither SLI or Crossfire is available for AGP systems, while both place extra demands on the system’s power supply.

The terms above relate to the physical aspects of a graphics card. However, you still need to know about the display properties of the graphics card to help you decide which is best for you and to get the most out of it.


Backview of graphics card connectors: S-Video, DVI, HD-15

AGP Slot

PCI Slot architecture

ATI Graphics Processing Unit

Nvidia Graphics Processing Unit

Graphics cards in SLi-mode