Who saw in practice the power of crossfire vs SLI?

Question

Video cards

I can't understand Nvidia has cuda technology.
And Radeons don't have strict requirements for the second video.
Crossfire and Sly are not equal.
sli - up to three vidyuhi (does it really give something?)
and only two in crossfire?
and how to find a list of games that only support sli without crossfire
or only crossfire and do not support sly?

Answer 1

Nothing.
That SLI, that Crossfire will not give a 2x performance increase.
And 1 older generation card will be better than 2 younger ones.
Not worth the candle game, do not bother.