Radeon 6850 and 6870 Crossfire inquiry - brand and wattage?

They generally should be of the same model. You can mix brand names.

Generally, it is best if both of the are the same like two HD 6850s, but you can pair up a HD 6850 with a HD 6870 if you wanted to. However, you'll be wasting some of the HD 6870's performance. Also, if one card has 1GB of VRAM and the other has 2GB of VRAM, then that extra 1GB of VRAM on the other card will be wasted since games have to load the same textures into each video card.

See following review: http://www.xbitlabs.com/articles/video/display/radeon-h...

Ideally exact same brand / model ... think of it this way, if ya have a problem and need tech support, the tech is gonna tell ya its the other guys problem.

Read this:

http://www.guru3d.com/article/radeon-hd-6850-6870-cross...

http://www.guru3d.com/article/radeon-hd-6850-6870-cross...

here's some info comparing the various cards:

Card 570 580 570 SLI 580 SLI 6950 6970 6950 X-fire 6970 X-fire

Guru3D
COD-MW 148 168 230 265 127 140 150 165
Bad Company 2 56 67 103 108 50 56 96 108
Dirt 2 80 96 138 149 72 77 131 140
Far Cry 2 85 104 153 164 76 83 147 161
Metro 2033 27 33 54 65 25 28 50 56
Dawn of Discovery 74 86 109 112 78 85 90 98
Crysis Warhead 54 62 86 90 51 57 87 97
Total 524 616 873 953 479 526 751 825

Cost $350 $510 $700 $1,020 $300 $380 $600 $760
$ per frame $0.67 $0.83 $0.80 $1.07 $0.63 $0.72 $0.80 $0.92

570 scaled 167%
6950 scaled 157%