ATI EyeFinity Technology (Now AMD EyeFinity) supports multiple video cards on the same System.
They are a moving company -- nothing to do with the ATI video cards.
ATI (Array Technology Industry) was an organisation engaged in development of Graphic Cards & Controllers. ATI was acquired by AMD in 2006 and now ATI name is longer used.
NVDIA SLI and ATI crossfire
That would depend greatly as to how far back do you want to go? Video Cards (NVIDIA, ATI, to name a couple etc), Video Capture Card, ATI Video Cards, PCI Video Card ... are just a few of the types, not to mention the various models of each card that exists.
One can purchase an ATI video card from brick and mortar stores or online shops. Places like Tiger Direct, eBay, Best Buy and Amazon offer ATI video cards.
For Nvidia Cards is Scalable Link Interface(SLI)For ATI its CrossFireX.
SLI or CrossfireNvidia - SLI ( Scalable Link Interface )AMD/ATi - CrossFireSLI and CrossFire
Yes you can use an ati video card in a sli motherboard, however you cannot put two ati graphics cards in that motherboard and run them in sli. As far as putting one in and just running it single your ok. You would need a motherboard that supports Crossfire to run two ati graphics cards together.
any pci or pci-e video card. such as ATI Radeon video cards (not agp ones) or NVidia GeForce video cards (again, excluding the agp ones)
nVidia and ATi both support valve games.
Anywhere from 750 to 100 watts if they are high-end video cards, like a NVIDIA 460 or ATI 6870.