Problem with dual Radeon 6950

[mrpeterc]

Hi, sorry if this is not the right place to post,

 I am having trouble configuring a MSI 870-G45 mb, AMD Sempron 140 CPU and dual Radeon 6950s.  When I run one card only I get video and can configure  Ubuntu 11.04, when I add a second card I get no video signal from startup, I have hdd activity and power lights but no signal.  I am  puzzled, can someone offer some suggestions?   Thanks in advance.

[papamo]

Sorry I can't offer any help but I have 4 6950's on the way so any information would be helpful

[mrpeterc]

I will post if I find something that helps.  Good luck, to both of us.

[unmitigated]

Have you tried running off the second card only?  Also are you running a dummy plug in the card that isn't running your monitor?

[mrpeterc]

I have run with both cards. seperately. they both work.  I had read a post where you didn't need the plug.  Do I need to use the plug?  Thanks for the resonse.

[einsteinx2]

I just built 3 rigs that are almost exactly the same as yours, just different brand motherboard (ASRock mobo, Sempron 140, 2x Radeon 6950). I'm also using Ubuntu for my rigs. I had no problems simply putting both cards in and starting the install with a monitor plugged only into the top card (the one in the real 16x slot). I'm not using any dummy plug in the second card. Also not using CrossfireX connector.

It sounds to me like the most likely issue is some default setting on that motherboard that is messing with the default video card when two are connected. Have you tried plugging your monitor into the second card (and on that note, have you tried some of the other video outputs on the two cards)? Also, dig through the bios settings to see anything related to the default video device. Sometimes it has settings like PCI-E, PCI, Integrated, etc. Try some different settings from the default.

Also, if you're using crossfire, try without. If you aren't, try with the crossover connector. Basically trial and error every option you can think of.

One other thing I just thought of, what happens when you start the machine with only one video card in, but in the second PCI-E slot? Could possibly be a bad slot?

[mrpeterc]

I have tried with both cards in different slots, they work seperately.  I will check the bios settings, thanks for the reply.