How does mixing cards in xfire work?

[breadturbo]

I've got 3x R290x in my main comp, all at 1000/1250.

Now in my second here at work I have one 290x (1000/1250) soon to be joined
by an R290 (maybe 2), I know the 290x will declock to the slower cards (975/1250) but what about the shaders etc? does any of that change?

Also, ya reckon a [email protected] will bottleneck 3x 290s?

ta

 

[LtMatt]

A little bit maybe in certain titles. Generally speaking it should be ok though. You'll have no worries under Mantle that's for sure. If you can up the overclock a bit to 4-6-5Ghz then that will help.

 

[Drangueos]

The 290x will not downclock to the 290 speeds, a crossfire between 290X and a 290 will be faster than 2x290 and slower than 2x290X.

Probably the [email protected] will bottleneck 3x290, since you already have cards some cards, you can test, just run the most demanding games that you have and see if all cards reach close to 99% usage.

 

[tommybhoy]

The 290x will not downclock to the 290 speeds, a crossfire between 290X and a 290 will be faster than 2x290 and slower than 2x290X.

Strictly speaking it won't downclock, but the 290X won't match core utilization 100%-outwith synthetic BM's(in games it'll generally run 93%290X/100%290).
^
(based on theoretical scaling@100%)

If you overclock the 290 about 7-10 % over 290X stock clocks, gpu usage will equalize=290X CrossFire stock performance.



Get a hold of an exceptionally good clocking 290 and your laughing providing your 290X can hold a decent clock.

 

[breadturbo]

Thanks for the replies folks
Ill see about upping the 3820, harder than the 3930 as the max multi on it is x43,
the 290 i've got is a tri-x, so ill have a play with it.