Video or graphics cards are what drive the generation of video graphics on your display. Nowadays, they are heavily used to render 3D graphics (PC gaming) or hardware-accelerated video decoding of HD content (Blu-ray movies, MPEG-4, etc) and flash content (YouTube, Hulu, Vimeo, etc).
Photo by .dr4gon
Testing a Broken Video Card
Video cards can break for any number of reasons including old age, overheating, shorting, or physical damage. If your video card is truly broken, it is likely you will not be able to do any of the functions named above. How can you tell if it’s really broken? The best way is to work through your problem step by step. First, make sure your video card fits your computer and is getting adequate power if it requires an external power source from a 6 or 8-pin connector(s). If it still does not work and your computer has integrated graphics, remove your video card and plug your display directly into your motherboard. If you get video, then your video card is broken. If you do not have integrated graphics and you have another card, try switching the two and seeing if your video returns.
The best check for performance is a standardized benchmark such as Futuremark’s 3DMark Vantage or older 3DMark06 suite of tests. Some other ways of testing your video card involve running standardized loops of some PC games, but 3DMarks tests are comprehensive, widely accepted, and provide a pretty good baseline to compare with other cards and systems. One of the problems with 3DMark however is that the final score is quite CPU based so you may have to compare individual scores to truly determine performance when comparing across different systems. Futuremark has a huge database called ORB, where scores are archived and can be browsed.
Testing stability goes hand in hand with performance. At stock settings, your computer (and video card) should be 100% stable. If it is not, something is wrong. You should have no problems running 3DMark. In other words, it may be slow, but it should not crash or cause artifacts on your screen. Testing stability becomes extra important when overclocking your video card. One of the best tests for stability is FurMark which is a free simple stress-testing program which tests stability by full stressing the card. If your card has a slight instability or inadequate cooling, FurMark will find it!
Monitoring Your Video Card
In addition to testing stability, it is equally important to closely monitor your video card. There are several good programs to do this.
GPU-Z: The most popular and free simple graphics card information and monitoring software. It is great for certifying clock speeds, checking your video card, monitoring temperature, and learning more than you would ever need to know about your card.
RivaTuner: The most popular overclocking tool for graphics cards. It also has a nice GUI and temperature monitoring application for checking clock speeds, temperatures, and fan speeds.
ATI Catalyst Control Center Driver Package: This is included in all ATI driver suites (CCC). Under the OverDrive tab, is a monitor for clock speeds, temperatures, and fan speeds. You can use this to tune your video card. Again, this will only work for ATI cards.
As far as I know, Nvidia does not have any monitoring built into their drivers. If you know differently, please let us know in the comments!