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Thread Starter 
(See rig specs below)

Background On Issue: I recently upgraded to a 30” Dell monitor and started playing Battlefield 3 on 2056x1600 at 60 hz. The downside to this was that I had to take the graphics down to low in order to get frame rates that I could stand. So I decided recently to invest in a second HD 6950 to crossfire in order to get the graphics quality back to what I was used to. I inadvertently purchased a used 1 GB and my current card is a 2 GB but decided to XFire them anyway and see what happens (I had 14 day return time.) Also, after researching it online for a while, I was unable to find anything that said you could not crossfire the cards, only that both cards would utilize only 1 GB of VRam each. So I figure two 1GB HD 6950 in crossfire should beat a single 2GB HD 6950, right?

I have easily done 5 hours of reading and 15 hours of troubleshooting including any tweak/setting I could find online and cannot seem to get these things working properly. All of my equipment is Crossfire capable according to manufacturers. I have reconfigured them on the motherboard, and verified that both cards work independently. I have tried clean Catalyst driver swaps of all recommended versions including 11.10, 11.10 + 11.9 CAP 4, 12.1, 12.4, 12.10, 13.1, 13.1 + 12.11 CAP 2… each driver set gave me a little bit different result but no success. I have installed latest Direct X, BOIS on MOBO, & disabled Intel Hyperthreading. I have played with every graphics setting/clocking setting available in game, on CCC, and elsewhere as well as countless other BOIS/windows/etc. tweaks.

Nothing I can do will give me any marked improvement over disabling Crossfire and running off of the single HD6950 2GB. With certain drivers I was able to achieve a slightly better graphics setting, but with marginally better performance and usually stability problems (stuttering, etc.) According to Afterburner on screen, both cards hover around 50% rarely making it up to 70% or beyond (also, I only have access to GPU 2 memory at around 2 GB whereas I have seen Afterburner crossfire screenshots online where it shows both GPU 01 & 02 mem. usage.)

If anyone can offer any suggestions on how to get these cards working properly I would truly appreciate it. I have 2 days to decide whether or not to return the second card. I would be happy to provide logs/screenshots/video dumps.

Three related specific questions:

1.) Is this proof that one cannot crossfire a 1GB and a 2 GB card?

2.) When two cards are in crossfire, should GPU usage be in the 90%s while in game, similar to the GPU usage of a single card while in the same scenario is?

3.) GPU-Z indicates that one card is in 16x PCIe and the other is in 8x PCIe. Could this be a problem and does anyone know how to fix it (mobo spec. says both slots are 16x)

Graphics Card
- Sapphire ATI Radeon HD 6950 (2) 1 GB & 2 GB
AMD Catalyst Driver Version, and Driver History
- 13.1, 12.11 CAP 2
Operating System
- Windows 7 64-Bit, DX 11, .net 4 Framework
Motherboard or System Make & Model
- ECS X58B-A, latest BOIS (v 05/04/2010)
Power Supply
- Corsair TX750W
Display Device(s) and Connection(s) Used
- Dell 3007WFP (2056x1600, 60hz)

CPU Details
- Intel i7 x58
System Memory Type & Amount
- (3) Kingston DDR3 2gb
Additional Hardware
- Antec 900 Case, Coolermaster v8