Problems with 2 x ATI HD6900 crossfire

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chrislouis

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Sep 26, 2014
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When i activate crossfire this is making my gfx perform bad compared to only a single gfx card. i have i7 950 CPU and 1000W PSU. what do u think is the problem?
 
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sincreator

sincreator

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May 27, 2009
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Quad crossfire and SLI have always had issues with stuttering, and just working properly overall. From one game to the next it is hit or miss. Most people will recommend 2 GPU's total for crossfire/SLI. Maybe 3 for SLI. You do know that you are trying to run quad crossfire right? Each 6990 has 2 GPU's.

Start reading at the second paragraph: http://www.guru3d.com/articles_pages/his_radeon_hd_6990_crossfire_review,23.html
 
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MkGriff1492

MkGriff1492

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Jun 30, 2014
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Check your motherboard to make sure it doesn't require an additional 4 pin power connected for CF. You would see it above the first pci-e slot. Make sure the CF bridge is attached correctly. I always use both but you really need one. Update drivers!!! Also if the second 6990 is an older card and clocked lower then the top GFX card you will need to overclock the bottom card to match your top GFX card. If you don't CF will underclock the top card to match the bottom card. Also the game needs to support CF to work.
 
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sincreator

sincreator

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3dmark won't show the problem though. That is one area that the drivers are always optimised, and won't show the issues he is having with games. Look at the review I posted to see what I mean.

 
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chrislouis

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Sep 26, 2014
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Correction guys, i have the HD6900.

After i activate the crossfire i check my AMD Overdrive:

1st card shows: 450 mhz GPU and 1250 MHz memory
2nd card shows: 0 at both.

will this change when beeing ingame or what?
 
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sincreator

sincreator

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May 27, 2009
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Yes it changes when a load is put on the graphics card. The second GPU lays dormant to save power until you need it. The clocks you are seeing is also just idle clocks, not your load clocks.

 
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chrislouis

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Sep 26, 2014
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Still have the same problems. Performance are so bad when i activate both cards. is my CPU bottlenecking? i have only 6 gig ram installed on my PC too. bcs of some defective i have.
 
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