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Struggling with Crossfire on the new build

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June 2, 2011 3:36:05 AM

Thanks for your help!

The issue pertains to my Asus P8P67 WS Revolution Motherboard and 2 Radeon R6970 Graphics cards.

There are 2 sets of PCI Express slots (2 blue and 2 black, in alternating colors). I have checked the vendor manuals and websites, but I am unsure if the graphics cards are supposed to be installed blue-black or blue-blue/black-black.

If I install the cards with a slot in between, then the Crossfire bridges included with the motherboard and graphics cards don't reach. If I install the cards on adjacent slots, which allows the bridge to fit, one of the card's side fan seems to be blocked. Should I be looking for a longer Crossfire bridge, or am I supposed to install the cards in adjacent slots?

Here is an image for your reference:

Thanks so much, I really appreciate it.
a c 136 B Homebuilt system
a b U Graphics card
a c 91 V Motherboard
June 2, 2011 5:13:23 AM

install them in adjacent slots


and then check the temps in CCC
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June 2, 2011 7:44:38 AM

Yup, scanning the plate on Asus website, you will be running crossfire at x8/x8, a single card in the first pcie x16 slot would run at 16x, but for multi-card setups, its half speed man, still good enough though
Moto
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June 2, 2011 1:25:25 PM

Thank you for your replies.

I am not certain, but I recall reading that the expansion slots are all 16x (I’m at work now, so I can’t check until later). Is that information helpful to you? Would this mean that there isn’t a performance loss by placing the cards in adjacent slots?

If possible, I would prefer to not lose any performance (especially not by half). If there is a performance loss by placing the cards in adjacent slots, do you know of any other solutions? Perhaps longer Crossfire bridges?
Finally, if there isn’t a performance loss by putting the cards next to each other, does blocking one of the card’s side fan cause any issues (in your experience)?

Thank you again. From someone who is still learning how to build computers, I cannot say enough about how much I appreciate your help.

Best,
Diaa
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Best solution

a b B Homebuilt system
a b U Graphics card
a b V Motherboard
June 2, 2011 6:49:23 PM

If you read the specs tab on here http://www.asus.com/Motherboards/Intel_Socket_1155/P8P6...
there are four x16 lanes, however, when you put two cards in the mobo, it 'decides' to run the cards at x8 in tandem, dont be put off by reading flat numbers and thinking oh, its only half the performance,
I'm not up to speed on gfx ins and outs that much myself but the 'loss' by going x8/x8 is not that great in real applications although on paper/screen it looks awful lol, on the other hand, my Mobo would run crossfire at 16/4 which would truly be pointless, and some mobo's only offer 16/1,
your mobo is balanced at x8/x8, trust in the force :) 

Moto
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June 2, 2011 7:08:27 PM

Thank you so much for your response Moto. I read those exact tech specifications, but just didn’t realize what I was looking at; thanks for taking the time out to explain all of this to me.

If I were to find a longer Crossfire bridge, would I be able to retain the 16x speeds? My plan would be to put a card in the first slot, skip a slot, and then fill put a card in the third one. If anything, this may also help out with ventilation of the graphics cards.

If so, do you know where I might find a longer Crossfire bridge? I’ve looked online, but with limited results.

I appreciate it,

~Diaa
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June 2, 2011 7:24:11 PM

No, regardless of the pci slot used, the mobo will always run crossfire at x8/x8 if your using adjacent slots
I'm unaware of any longer bridges, they would certainly be useful to a lot of people, and yes, having the space between card would be good for airflow
just be glad your not doing two of these anytime soon http://www.geektv.info/video/tech-review/asus-amd-radeo...
I will be......
Moto
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June 2, 2011 11:07:30 PM

Best answer selected by Diaa.
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June 2, 2011 11:20:05 PM

This is false. the WS Revolution has an NF200 bridge and can run x16/x16. I believe you need to use the blue first and third slots. you will need a longer crossfire bridge.

the editors ran into the same problem in their $2000 march system build marathon
http://www.tomshardware.com/reviews/intel-sandy-bridge-...
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a b V Motherboard
June 3, 2011 7:30:10 AM

Gerat find there! I think I'll need one of those myself for the Asus 6950 Direct CuII's :p 
hope it goes well man, and Thank you for B.a
Moto
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!