How to buy a graphics card (*Revised on 12/07/08*)

Manufacturers rarely create their own graphics cards, rather they buy "reference" boards of a specific chipset from NVidia, ATI or another manufacturer and then modify/overclock/etc. to meet their own criteria or pricepoints. Because of this, you may see say one Nvidia Geforce 7600 from one manufacturer that has 256MB of memory while another has 512. GPU cooling fans/passive heat sinks also contribute to a degree of variability in card size and running temperature, you must consider these as well as other factors when making your purchasing decision.

Graphics card Interface - There are 3 typical graphics card interfaces, or slots inside your computer that accept graphics cards. The availability of these slots can affect your choice of graphics cards significantly. Check your computer manual/the manufacturer's website for information on your particular computer model, it should indicate the make and number of the expansion slots in your computer.

PCI (Peripheral Component Interconnect) - an interface that supplanted ISA for graphics cards and other add-in cards years ago, it is typically medium length white or off-white slot inside your computer case. No new graphics cards are compatible with the standard PCI slot, so you will be limited to older cards such as the Nvidia GeForce FX series, or the GeForce 6 series, or the Radeon 9000 series of graphics cards. You will typically have at least an AGP slot available, unless your computer is a low-end budget model a few years old, or more than 5 years old. Needless to say, where graphics cards are concerned, PCI is the slowest connection interface of the 3.

AGP (Accelerated Graphics Port) - First integrated into motherboards in 1997, AGP slots provide a decent speed improvement over standard PCI. AGP is almost totally phased out, and while you can buy Nvidia 7600's etc in an AGP flavor, AGP graphics card choices are rapidly dwindling.

PCI-Express/PCI-Express 2.0 - The current standard for graphics cards, providing several times the bandwidth capacity of the AGP bus, graphics cards are sure to sit in the PCI-E bus in the near future. A PCI-E variant of a card will typically be somewhat faster than the same AGP variant in a similar system due to increased bandwidth. Any computer manufactured within the last 3 or 4 years should include at least 1 PCI-E slot, if your computer does not, and you plan to do multimedia work or moderate to serious gaming in the near future, I would submit to you that it might be time for an upgrade - current computer prices provide the most bang for your buck in quite a while.

Graphics Memory size/speed - You always want to buy the variant of your chosen card that has the most memory - lowend cards may have as little as 128MB of onboard memory while mainstream usually come equipped with 256MB or more of memory, and workhorse and extreme performance cards ship with 320MB+ of graphics memory. For general users, more video memory means smoother general and video performance, and access to higher resolutions, and the possibility of utilizing multiple monitors simultaneously, for gamers more video memory means both higher game resolution, and the ability to use higher resolution textures and additional filtering techniques such as AA(Anti-Aliasing, smooths jagged edges of 3D images by introducing intermediary colors between 2 points) and AF(Anistropic Filtering - ensures that textures do not become blurry as they are rendered out to the horizon). More important than the amount of memory(especially for higher end users), is the speed of the memory, graphics memory typically comes in 3 speeds - DDR(Double-Data Rate, rarely anymore excepting very low end cards), DDR2(Standard for mainstream cards) and GDDR3 - GDDR3 is substantially faster than vanilla DDR2 memory, the "G" prefix denotes that the card uses "Graphics" DDR3 which is an upgraded DDR2 memory spec' that facilitates increased performance when running graphics code, and runs somewhat cooler than DDR2 memory. While more system memory usually equates to better system performance, this is not true of graphics cards. an Nvidia 7600 video card with 512MB of memory may have twice the memory of an ATI Radeon X850xt graphics card, the the X850XT uses faster memory, has more shader pipelines (I will discuss this later) and better GPU (Graphics Processing Unit) and memory clock speeds, and so it will outperform the Nvidia card with more memory. If at all possible, pay the difference for the variant of your card with more/faster memory, you will not regret it.

Graphics Card/Memory bus width - Memory width is typical 128/256/320 bit. Anything below the workhorse level typically uses 128bit memory, but opt for 256bit if at all possible - the bus is the "information highway" of your graphics card, and the higher the bit rating, the more lanes that highway has, and it can feed your graphics card at a higher rate.

Graphics Card size/Cooling - While low-end cards will fit in just about any case and don't generate much heat, mainstream or high end cards will require adequate room inside your case, and space between other add-in peripherals for decent airflow, and don't even think about going for an enthusiast case unless you have a very roomy mid-tower case or a normal full tower, these cards are typically quite large and thick, and require better than average cooling under stress. Be sure to open your case and get a feel for the room between expansion slots before you buy + check out specs and pictures of your card before purchase. That case that was nice and quiet with the onboard video will get a bit buzzier and hotter with a standalone graphics card, so make sure you have adequate cooling - an improperly cooled card (any component for that matter) will have a significantly shorter useful life than one with adequate cooling.

Power Requirements - Unless you opt for a low-end graphics card, the power supply or PSU that came with your computer likely won't provide enough power for your new graphics card as well as the rest of your components. A typical low end graphics card will require a 200 or 250 watt power supply, while a mainstrem will require a 450 watt or better power supply with high ends recommending a 550 watt or better(I recommend 650+ watts for high end cards and 750+ for enthusiast). A good policy is to take the recommended power rating and add 100 watts to that to factor in current computer components and leave room for future upgrades. Another factor to consider is the 12v rail rating of your PSU. For mainstream and enthusiast graphics cards, the manufacturer will usually make a recommendation for the number of amps you should have on the 12v rail - this is typically listed on the back of the PSU box or in the specifications. Expect to spend $80+ on a decent power supply, and do not be tempted by cheap power supplies, your power supply is perhaps the most important component of your entire computer, a PSU can take a whole computer with it when it goes, then that bargain doesn't look so great next to the prospect of a new computer purchase. Antec is largely the standard for reliability in power supplies, and they make a solid, quality product at a reasonable price, other reputable brands include PC Power and Cooling and Enermax.

Windows Vista Compatibility - Windows Vista brings with it the new Aero interface and higher memory and graphics card requirements than ever before, the basic 32MB+ video cards of Windows 98 and XP aren't going to cut it for this new interface, driving many people to consider upgrades. Make sure you check the website for your desired graphics card to make sure there is a fairly recent Windows Vista driver available if you are running/plan to run Windows Vista.

Recommended online retailers. - I recommend you check out the following online retailers for graphics cards as well as other computer components:
NewEgg
Tiger Direct
ZipZoomFly


Having a dedicated graphics card can mean the difference between just using your computer, and getting the most out of it. With the large number of makes and models out there, you are sure to find a graphics card that meets your needs and budget, and even sub $300 can provide plenty of performance.