I have a VisionTek Radeon HD 6950 2 GB and a PNY GTX 470 Enthusiast and decided to get another one of one of these 2 GPU's, to prepare for BF3.
3 questions I have though.
(1) Which setup would be faster? 2 6950's or 2 GTX 470's?
(2) If I bought the same GPU but from a different manufacturer, will I still be able to Crossfire/SLI it? I heard you can't.
(3) How many Watts would my PSU need to run the setup?
1) 6950s would be much faster. They are more powerful individually, and CF scales better than SLI.
2) You can CF/SLI any two cards that have the same core, i.e. any two 6950 2GB cards or any 470 1280MB cards. I've heard that certain combinations of cards may be unstable together, but you can usually fix this by making sure they have the same BIOS on them.
3)You could run either setup on a quality[/i ]650w unit, and a 750w PSU would give you all the overclocking headroom you would need.
You did mention BF3 specifically, and I must qualify what I said by adding that the open beta was horribly buggy for both configs(I run SLI and my roomie runs CF), and Nvidia was performing a little better than AMD, but my guess is that that will all be resolved within a month of release.
If you want to run SLI or Crossfire, you only need to get the same card model, not the exact manufacturer model. IE. any 6950 will work, but not a 6870 or 6970. This is an oversimplification of whats going on but that's pretty accurate.
As far as which is better - there are probably situations where one is faster than the other and vice versa. They cost the same from what I can find online. The radeon is current gen and the 470 is last years model though. Personally I think 1 6950 would do it for bf3, but I don't know the res you are running.
Re: power, I believe 600 watts for the 6950s and maybe 700+ watts for the 470? I know its more than the 460s and I just upgraded a PC to a 650 watt for those cards. Read the product specs for both cards at the manufacturers for their requirements.
Well, I plan to max out EVERYTHING at 60 fps, except AA & AF. (Which 2 6950's should be fine with that) And I will also be playing in 1920x1080. The card did 'okay' by itself with a resolution of 1920x1080 running at a minimum of 35 FPS and a maximum of 80, but then again that was BETA. I also have a 850w PSU so I should be fine with that.