290x CF underperformance

[MatMatthewMat]

Hey there. Budy of mine helped me yesterday with buidling/upgrading my old pc. I was rocking am3+ 990fxa-ud3 mobo, with fx8350. I have two different 290x cards. One is from Sapphire with reference cooler. Second card is manufactured by Asus and has aftermarket cooler. Both share the exact same specification. Both works like a charm, when CF option is not enabled.... I have tried multiple drivers. I have even tried catalyst 13.12, which worked in a triple monitor setup back in a day on 8350, and Win 8. No luck at all. Older the driver I was using, the worse performace did I get. I have tried installing driver after clean driver uninstall (ddu), I have tried to change the order of cards... Undervolting, bumping up power limit, underclocking. No luck. While I was fooling around in a GPU-Z I found out two insteresting information. One is, that both cards have different type of memory, which according to few internet posts shouldnt be a problem at all. Another thing that I found odd was a setting on one of two cards: "board power limit" which is set to 50watt. Do u have any suggestions? I will post avreage fps with cf on/off and screenshots from gpu-z when I get home from school. One thing is sure. I shouldnt pull the trigger and jumped to upgrading my pc before brainstrming the reason, why my cards wont work together as they are supposed to...

Thanks in advance for any suggestions. I would like to make it work. I dont like an idea of selling these cards for just a fraction of a buying price.

 

[4745454b]

My ideas. First, that board has more than two PCIe slots. Make sure you are using the right ones. Avoid any 4x electrical slots. 16x or 8x only. Second, do you have the power for all this? 290X cards are 300W cards, so you need 600W JUST for the cards. You'll need another 125W for the CPU. You'll need more than this for any OCing you are doing. If you have a 750W PSU, you don't have enough power. Finally, the 8350 would have enough trouble driving even one 290X, asking it to drive two might not work as well as you think.

You said they work just fine with CF disabled, you never said what happens when you turn it on. What errors are you getting?