as a single card , this be excellent , it run cool and quiet , and the shader CAN be unlock to the level of a 6970 . it also have a bio switch which be handy and make unlock the shader a much safer process . after run a few benchmark and feeling pretty happy about the single card purchase , I install the second -lrb- matching -rrb- 6950 Dirt 3 edition , and this be where the fun begin . there be a issue with slus and crossfire configuration know as microstuttering . if you be not familiar with it , please google it and check it out . there be a excellent article on tomshardware about it , where they show you some very interesting graph explain what microstuttering be and what cause it , and also how certain card be more prone to the issue than other . before you plan on run these card in crossfire , please do a little research and decide if you thing this be something you can deal with . -lrb- ... -rrb- I be vaguely aware of the issue , but have not ever do any research on it . after install each card into the two x16 pci-e slot on my motherboard , I boot up and start run benchmark . it turn out , these card scale very well , and in unigine and 3dmark11 I be see about a 70-80 % increase in framerate . however , this be where I start to notice the stuttering that take place , and although you may be get framerate of 60 or 80 fp , it be not a smooth and fluid experience at all . benchmark tool be one thing , but I do not think any of we buy these card to hang out and watch benchmarking test and demo . so I start test this out with game . First off , my favorite game be Starcraft 2 . if you carefully watch you unit move in this game , you can see the microstuttering . you can also see it in the begin intro where the spaceship fly past the planet . I attempt turn vsync on , enable triple buffering , restore the shader to stock , disable the overclock on the card , disable the overclock on my CPU , everything that forum suggest , and nothing seem to have a affect . to make sure that it be not a issue with a single card , I completely remove one of the 6950 's from my system . this solve the issue immediately . the next game I check out be Deus ex human evolution , which be one of the AMD flagship game . microstutter be MUCH worse in Deus ex . turn on vsync help quite a but but completely kill the framerate , make it a much choppier experience . with vsync disabled , you get awesome framerate , but terrible screen tear and of course significant microstuttering . at the end of the tom 's hardware article , they recommend spend you cash on a single fast card over two in SLI or crossfire because of this issue . I tend to agree with they . I purchase these card to replace a single gtx480 , and because the performance of one of these card be comparable to the gtx480 , it be not worth keep one of they . I be go to keep they for weekend , and if I be unable to resolve the microstuttering issue , I will be return both of they . it be true that you get awesome fp from these two card , but to I that be useless if gaming be not a smooth and fluid experience . I personally would rather have one great card run with less fp that deal with extremely high framerate with constant microstuttering . by the way , if anyone reading this review have any idea for I , please let I know , I really want this configuration to work . detail for my machine be list below : Proc : Phenom II x6 1090t @ 3.8 GHz Mobo : Asus Crosshair iv Formula RAM : 16 gb G-Skill Sniper ddr3 1600 Video : 2X Sapphire Radeon HD 6950 2GB SSD : Wester Digital 128 GB HDD : Seagate 1 tb PSU : Cooler Master Silent pro 850 fan : Cooler Master Hyper 212 + case : Antec DF-35