How To Crossfire Support? Good Video Card That Supports It?

[NNNNNNNNNos]

How Does Crossfire Support Work? Do i buy it? How do i get it?
What is a good graphics card that supports crossfire?
my parts- http://pcpartpicker.com/p/pZvrkL
budget 500$
i already have a good video card but nobody is selling it so i need one exactly like it

 

[Grimwinder]

1) You need a board that supports Crossfire.
2) You need 2 cards with the same core chip, most all newer model AMDs support crossfire (the "new" r9 280 has the same chip as the "older" HD 7850, so they will work together for example).
3) You need a PSU that supplies enough power and has enough power connectors for both cards.

Crossfire will use the GPUs of both cards to drive your display(s). The amount of effective vram available will be the amount of the lower of the 2 cards, if one has less vram that will be the effective amount used (the process will use that amount on both cards but they are mirroring the same job, thus the effective limitation).