Hi, I am attempting to overclock my gigabyte 7950's in crossfire (which I hear overclock like a beast). Every time I move the slider for the frequency up even a little bit I have stability problems and no game will play. I tried raising the voltage a little as well with no luck. so I have two questions:

1. Is it possible to overclock in crossfire mode and if so what am I doing wrong?

2. What is a surefire test to make sure a graphics card isn't faulty?

Thanks.

* I forgot to add that my PSU is a Corsair HX 1050 watt, CPU is a i5 2500k oc'd to 4.5 ghz, and mobo is an asrock prof fatality gen 3.

Try Individually overclocking the cards with crossfire disabled or the other card removed and see what luck you have. 

Have you tried MSI afterburner? Or are you just useing VECC.

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I5 3570K@4~5.0ghz: Gigabyte GA-Z77X-UD3H:Corsair Hydro H70w/Delta 240CFM Fan: 16GB Corsair Vengeance DDR-3 1600: 2 XFX Radeon 7950 @ 1150/1575 : Corsair AX 860 PSU: x2 WD Black 1TB HDD's: 90GB OCZ Agility 3:CL X-FI:Corsair 500R Arctic White Edition:3 22inch Asus monitors Eyefinity @ 5294x 1050(bezel comp) : Alienware Tact-X Keyboard: Naga Razer gaming mouse:Corsair Vengance 1500 Headset .

For OCing tests, use Furmark, Heaven, or any other program.. I use Furmark to test my OCs on my cards..

2 identical cards never OC the same, so maybe doing it on CFx is causing the crashes, so like Vantharas told you, test one by one..

Use MSI AfterBurner to do the OC, like this: move the slider to increase, let's say, 5-10Mhz, save, and run Furmark (or the program you have chosen).. If artifacts/blue screens shows up, that's the limit and you have to step back.. Of course, this is on each card, not CFx..

Sorry can't be more helpful on the CFx OCing, but I only have one card, and always have.. But for the OC, sure..

 

Best regards..

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8320 @ 4,5 / 990FXA UD5 / 7950 @ 1150-6200 / Switch 810 / H80 / 16 GB RAM / 23" 5760x1080 / SSD 64GB RAID0 / Tr2 750W

Okay thanks for the suggestions. I am just hoping my cards aren't faulty as I was getting unusually low framerates in some games. Just cause 2 dark tower benchmark only averaged 40 fps with all settings maxed and vsync off. I never got any artifacts or weird things like that though...

Just because your card can't overclock doesn't make it faulty, product binning makes overclocking possible and is not a guarantee that a card will be able to overclock, it means that any given card is guaranteed to work at the frequencies set to it by the manufacturer.

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Crosshair IV Formula, Phenom II x4 965 w/ Corsair H60, 8 GiB OCZ Platinum DDR3 1600, XFX HD 7970 Ghz, 512GB Vertex 4, 256GB Vector, 240GB Agility 3, Creative X-Fi Titanium w/ Creative Gigaworks S750, SeaSonic X750, HP ZR2440w, Win 7 Ultimate x64