Correct Crossfire Setup

[Guest]

Folks, I just bought my first dual gfx card computer--two 6850s sitting in a MSI 790FX-GD70 motherboard. Does it matter which two PCIE slots I use? They're all the same speed, but someone told me that for true crossfire you must use PCIE 1 and PCIE 3. The problem is that the crossfire cable I have will not reach that far! I can do slots 1&2 easily, but it just plain won't reach all the way to 3! Am I boned?

 

[wiinippongamer]

Slots 1 & 3 Are x16, and slot 2 and 4 are x8.

There should be two crossfire bridges inside the motherboard box, those are long enough to reach to the third slot ( I have the same motherboard)but the ones that come with the gpus mostly aren't.

The fact that slots 3 and 4 are x8 doesn't mean the cards will run at half their speed, there's only 2-3% difference in performance, actually most motherboards are only capable of X8/x8, only a handful of boards like the GD70 are capable of full x16/x16.

 

[Guest]

Thanks for the reply, Wii! I thought there were supposed to be crossfire cables too, but there were none in the box... No stores around here carry them, either. Ah well, I suppose I'll have to order it and wait.

 

[wiinippongamer]

This is what you're looking for:

If you bought the motherboard brand new and unopened then they HAVE to be there.

 

[Guest]

Any idea what the quickest way to get one might be?

 

[Guest]

Yeah, it says in the manual that they are supposed to be in the box, but they're definitely not... Brand new, unopened, not refurb'd, from Newegg.

 

[wiinippongamer]

If you don't have them best is just to leave it as is, you won't notice 2% less performance.There aren't any adverse effects neither

 

[Guest]

I can run them in 1&2 in Crossfire then? I thought you were saying it had to be 1&3, or 2&4 with a 3% performance drop.

 

[wiinippongamer]

If you run a single card in slots 1 or 3 it'll run at x16, but if you run it on slots 2 or 4 it'll run at x8.

If you put one of the cards on an x16 slot an the other on a x8 slots they'll both automatically run at x8.

 

[Guest]

Gotcha. You've been most helpful, man!