Crossfire Crappy FPS. Pci express bottleneck? How much?

[Juliogol]

HI guys,

So I've been struggling to get a R9 280x CF to work properly, but I am about to give up. I think that my problem is that my motherboard has a PCI Express 3.0 at 16x but the other one functions at 2.0 4x when crossfiring.

I think that is why I'm not seeing the two 280x perform as they should. I game at 1080p, mostly BF4 and get 70-110 FPS on medium settings...

What do you guys think, it the PCI at 4x bottlenecking my 2nd GPU so bad that I get these results? If I upgrade the MOBO will I get better FPS?

Rest of my specs:

Core I5 2500k
12 GB RAM
120 GB SSD
MOBO Gigabyte h67m-ud2h-b3

I appreciate if you can help me out here!

 

[Vanth]

Yes, I believe this is what's happening here. Make sure that the next mobo you get does have two fully dedicated X16 PCI express slots.

 

[Ketchup]

How do they compare with running the single card at 16?

But yes, for high-end cards running crossfire, you probably do want the Z chipset, which would give you 8x in Crossfire.

 

[Juliogol]

How do they compare with running the single card at 16?

But yes, for high-end cards running crossfire, you probably do want the Z chipset, which would give you 8x in Crossfire.

I get almost the same performance with one card than with crossfire.

EDIT: actually in BF3 with one card I get 100 FPS avg. With crossfire enabled I get 55 FPS AVG :S