Will a 7970 non-ghz edition crossfire with a 280x? Please read description!

[TechiGamer]

Hi !

I was taking a look on ebay and found a really good deal on a 280x. However, to my disappointment, my local retailer as well as MSI said that a r9 280x and 7970 OC edition will NOT crossfire successfully. Seems quite controversial since nearly every forum said you can ,yet these professional companies say I can't. I'm really confused at the moment. Can anyone please explain if it can or cannot?
What MSI said was that it has to be the same card. But I though that a 7970 and r9 280x are literally the same thing except for different clock frequencies.

So if such a small difference makes it unable to crossfire than how can a 7950 and 7970 crossfire? This is not making sense.

* Edit * I am trying to crossifre an r9 280x MSI and a gigabyte 7970 OC edition ( not ghz edition )

* Edit * I just phoned up NCIX techsupport and they said that it will crossfire, but the different bios will affect performance. How much loss in performance would I see in comparison to 2 7970's crossfired?

 

[Tcinator]

I recall in the past reading about having 2 x16 bus being split between the 2 card effectively giving it a x8 x8... and if you had a x16 and a x4 slot, the crossfire would run at x4 bandwidth and effectively split the x4 between the 2 cards making it x2 x2. and if you had a x16 slot and a x8 slot, it would run at a bandwidth of x8, splitting it between the 2 cards, giving each x4 of the bus.

I have no idea if this still holds true in all motherboards or just lower quality ones.

SO: if this is still the case, getting x16 x16 in any regard is still better than not.

 

[TechiGamer]

I recall in the past reading about having 2 x16 bus being split between the 2 card effectively giving it a x8 x8... and if you had a x16 and a x4 slot, the crossfire would run at x4 bandwidth and effectively split the x4 between the 2 cards making it x2 x2. and if you had a x16 slot and a x8 slot, it would run at a bandwidth of x8, splitting it between the 2 cards, giving each x4 of the bus.

I have no idea if this still holds true in all motherboards or just lower quality ones.

SO: if this is still the case, getting x16 x16 in any regard is still better than not.

Okay! So any recommendations?

 

[Tcinator]

http://pcpartpicker.com/parts/motherboard/#f=2,7&l=1000&qq=1&h=2,7&N=4,12&c=99&J=0,4&sort=d5

http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007627%20600438202%20600491547&IsNodeId=1&bop=And&Order=RATING&PageSize=20

Theres 2 lists. Don't have experience with any of those boards, but they are all Z97chipsets and are filtered by highest rating. Honestly any of those should be great. (the higher rated/ higher price) ones. Lol.