Firstly, I shall talk about the most important thing to keep in mind when you upgrade to a new graphics card and that is if your current system is compatible with it in the first place. Most graphics cards out today require a 16X PCI-e (known as PCI express) so you need to make sure that your motherboard has this slot. You can check your motherboard box, manual or website for these details. To look at, it is a dark brown slot which is slightly thinner and longer than the white PCI slots on your motherboard.
Next thing you need to look out for is your power supply. When you decide to buy a card, check out its Specifications on the website. It would mention the amount of power your card would require and a list of recommended power supplies. Generally this is not an issue if you are going for an entry-level graphics card which would require very less power. Mid-range and high-end cards would require one or two extra 6-pin power cables in order to support it. Remember if you do not have a power supply that can support your card you need to think about purchasing that even before you think of buying a card. Having adequate power is very important when you have a high end machine. Good power supply manufacturers (like Corsair, Zalman, Coolermaster,etc.) have certified power supplies with advanced load management functions, etc which is crucial when the graphics cards draw a lot of power.
Alright, now you have an idea about your power supply as well. Next thing to consider? Will your card fit into your cabinet in the first place?? High end cards are usually mammoth in size. Sometimes everything in your system seems to be fine except that your card does not fit into your cabinet. Make sure you check the dimensions of your card in the Specifications section on the website.
One more important factor to consider is cooling. High-end cards usually generate a lot of heat when playing games with maximum details and resolutions. Basically anything that "pushes" the card to its limits. Sometimes even when you are not playing games or watching movies (known as idling), your card could still be generating a significant amount of heat. The only way you can circumvent this is by having a cabinet that cools well. Two of the best gaming cabinet manufacturers I have come across are CoolerMaster and ThermalTake. Some of the gaming cabinets cost almost as much as a mid-range graphics card and could seem daunting at first but there is always a reason behind that price tag. Cooling is very important when it comes to the durability of your system. Remember its not just your card that is in question here but all the components of your computer as well.
There might be some other additional requirements that need to be looked out for to make sure that your system is compatible, but the ones mentioned above are the most relevant ones and the ones which people tend to forget.
Great! Now that we know our system is compatible with our card, let's have a look at what we should look for in the card itself and also answer the famous question "ATi or nVidia?".
I will not get into too many details on each and every parameter that needs to be considered when buying a card. You don't need to think that hard and lose hair. My intention is to clear out certain myths that people have. One of the most common ones is that if a graphics card has a greater memory, then it is a faster card. WRONG! That's not how it works. The most important factor is the Engine clock. The higher the engine clock, the better. The other thing you need to check is if it supports the latest technologies. Sometimes the latest technologies make the card more expensive in the beginning. A card having a high engine clock but supporting older technologies could cost the same as a card with a lower engine clock but which supports the latest technologies. This is when you make a decision between performance and quality respectively. I have come across this website which frequently reviews graphic cards and posts their fps (frames per second) online. http://www.videocardbenchmark.net/high_end_gpus.html
This could very well be a good reference point when selecting a card based on performance.
Lastly, I would like to just cover my views on the two most eminent graphic card manufacturers ie. ATi and nVidia. I have dealt with several graphic cards since many years and I what I mention here is only my perspective on the two manufacturers so opinions may differ. People are generally inclined towards nVidia because of the sheer support they have from various games. There are more number of games that endorse the nVidia logo than the ATi logo. What I am trying to convey here is that in reality, nVidia and ATi are both equally good. When you play games, you don't see much of a difference in image quality between the two cards. The reason you would want to pick up an nVidia card anyway is because of the support for PhysX, which ATi does not support. PhysX, initially owned by Aegia and later bought by nVidia, is a physics engine which uses a separate processor for performing calculations related to physics within a game. This could include the way a flag flutters, a wall is destroyed, the way a ball bounces off a wall, etc. When you don't have a PhysX engine, these calculations are performed by the CPU instead of the dedicated processor. What all this means is that if you have an nVidia card, it takes a little load off your CPU when you play games which include several physics calculations. Earlier, there was another reason to consider nVidia and that was the stereoscopic 3D support. But now glasses are available for ATi cards as well and so that is not a factor. Now a reason to consider ATi cards over nVidia cards is that ATi cards work at much lower temperatures than nVidia cards. I have confirmed this online and I have also experienced it myself. My earlier card, the nVidia GeForce 8800 Ultra used to idle at around 70 degrees C whereas my new card, the ATi 5750 HD idles at just 45 degrees C and is also a better performer. The maximum temperature reached by this card is around 55 degrees C as compared to 95 degrees C for the nVidia card. But this does not mean all cards heat up to this level. The room temperature at which you operate the card and the cooling system for your cabinet play vital roles in determining the actual idling an max temperatures but if you stay in a place where room temperatures could go above 35 degrees C, I would suggest you get a card which idles at lower temperatures. Also another thing is that ATi cards are generally cheaper than nVidia cards for the same performance.
For enthusiast gamers, there are several other aspects like SLi and Crossfire, which I will not be covering in this post. Hope my post helped you if you are planning on getting a new graphics card and if not, I hope you enjoyed reading it :)
