Crossfire x16 x4-Has anyone tried it?

Hey everyone,
I am currently using a H97-d3h and an r9 390. I am considering possibly purchasing a 2nd r9 390 for crossfire since I can get one at a very decent price. My main concern is that even though my motherboard is "crossfire capable" it makes me weary that the 2nd PCI-E slot runs at x4 speed/bandwidth. I have tried contacting both Gigabyte and AMD and they seem to pass the buck to each other-basically Gigabyte saying "you should ask AMD"(and rightly so imo) and AMD saying "you should consult your motherboard manufacturer".

I have tried to find threads/articles on the issue but the closest I have come across is the difference in performance between x16x8 and x4 slots but none of them are crossfire specific and do not take into account XDMA using the pci slots.

Has anyone out there actually tried running crossfire in a x16x4 configuration? I understand there'd be a performance penalty but is it significant enough to negate any benefits gained?

Thanks for your input everyone.

P.S. I do understand some peeps will simply say "upgrade your system etc" and I am planning to do a whole system overhaul perhaps at the end of the year/beginning of 2017. It is really to see if this is worth doing at this time.
 
Solution
10% performance loss pretty much over a 16x 16x config.

I fun 280x cf on the same configuration, on straight benches I'm getting straight up double bench scores (furmark)

These older cards run a bridge cable though which reduces bandwidth requirements on the second card.


I think you may have misunderstood my question-I'm not trying to go quad-Crossfire. I am merely trying to go 2x390 in crossfire but my motherboard only has 1 PCI-e 3x16 and 1 PCI-e 2x4 slot. Although it is crossfire certified and I do understand that there will be a bottleneck in the x4 slot I was wondering as to how much of a performance impact I'd be looking. I know it is not ideal and not as efficient as x8x8 config but still interested if its viable as all.
 
10% performance loss pretty much over a 16x 16x config.

I fun 280x cf on the same configuration, on straight benches I'm getting straight up double bench scores (furmark)

These older cards run a bridge cable though which reduces bandwidth requirements on the second card.
 
Solution


Thanks for the response Matt! If I'm only looking at a 10% loss that is more than acceptable perhaps its a viable option afterall!