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Tri-Fire 7970, 7970, 7950

N

nathancnc

n00b
Joined
Dec 8, 2012
Messages
14
I have (two) 7970 Ghz and (one) 7950 Boost. I cannot get 3 way crossfire to work , it tells me to plug in 2 crossfire bridges, even though I already did.

My motherboard supports 3 way SLI and CrossfireX

The cards are arranged like this:



------7970-------

(crossfire cable)

------7970-------

(crossfire cable)

------7950-------
 
Which motherboard are you using? Is the bios up to date?

Maybe try a different driver?

Also what does GPU-z report?
 
ASUS crosshair formula Z with 8350 piledriver cpu. latest bios from asus.

gpu-z detects all three cards, but crossfire is disabled in it.

I have tried both 12.10 and 12.11 beta
 
no, i am using the 1st, 2nd, and 3rd red pci-e slots. the 4th red pci-e slot is covered by the last card.
 
Are you powering the molex near the video cards? It looks like its labeled ezplug.
 
yes the molex is plugged in. I have a 1250 watt xfx gold power supply, and both the cpu 8 pin and cpu 4 pin plugged in aswell.
 
When i was setting up my 3x 7970's i had the same problem, turned out one of the crossfire bridges was faulty.
 
I'm not sure, but I think its because one is a 7950.... but I thought it would be compatible with the 7970. I have tried different bridges aswell.
 
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But I want my two 7970's to be the primary cards, since tr-fire does not scale as well to the third card.
 
Shouldn't there be a third bridge going from the 3rd to the 1st card?
 
It needs a third bridge? I saw online it only needs the two. I don't even have a bridge that is long enough to do that...
 
Since all of the cards can be mixed in crossfire it might be the 3rd pcie slot that's the problem. Check for bios updates for your MB and also look in the bios to see if there's any setting that activates/deactivates any of the slots.
 
How do you have the bridges connected? You need all 3 cards to have a bridge connected. You will need 2 crossfire cables. There is a few different ways to connect the cards. You can use the longer cable that comes with the mother board and go from card 1 to 3 then 2 to 1. Or 1 to 2 then to 3. I connect mine from 1 to 3 then to 2. This on a asus rampage IV but the process should be the same.

Edit:
NVM I seem how you had them connected missed that part. You could try swap that crossifre cables/cards around to see if you have a bad crossfire port.
 
Last edited:
the order of the cards... i'll try and explain, hope it makes sense...

It was simply the order of the cards, IO switched it so the 7950 was in the middle (had both crossfire connection populated, one to above 7970 one to below 7970) and it worked just fine.

I thought of this when I noticed how the board is actually wired. The 3rd red pci-e slot down the board is actually the 2nd one electrically, and the 2nd red pci-e slot is electrically the third one...and the 7950 has to be in the third slot electrically.....doesn't matter where is physical placement on the board is.
 
well good thing you solved it. I wasnt aware you could mix up cards for crossfire. Interesting.
 
Wow, I was following this thread and I'm glad you resolved your problem.
 
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