Geforce GTX 680 SLI

It will be a tight fight but it's perfectly fine.Of course the top card will be a little warmer because of the reduced airflow but it's fine.

No don't use the x8 slot.The GTX680 needs all the speed it can get from the x16 slot.

Use it in the x16 slot. Just make sure the temperatures don't go high, which shouldn't be. If it is too high though, you have to put it on the x8 slot.

I've never heard of the x16 slot allowing a card to heat up; where did you learn this?

Is this still an issue if you have two GPUs in xfire/sli in a set up that is 8x/8x (where the first slot is normally x16)

It's not that it's x16, but because using both x16 slots puts the cards right next to each other, so the top card doesn't get much air flow at all.

I personally recommend testing x8/x8 or even x16/x8. I ran my 470's that way and had nearly no loss in performance. I know the 680's are faster, but until you test it, you won't know. One benefit to keeping them cool is that they also are quieter.

Yah their is about less than 1/2 an inch of space between the cards in those type of mobo configurations.So they do heat up quite a bit above normal because of it.

I would think a GTX680 running at x8 would get about a 10%-20% performance hit.We don't even know yet how much the PCI-E 2.0 slots are,if any,bottlenecking these high end 3.0 cards.Could be more could not be at all.

But as bystander said you should test it in the x8 slot.Run some simple benchmarks in the x16 slot and then switch the card over to the x8 slot and see how much of a performance hit it takes.

That is the typical spacing for CF/SLI setups. There won't be an issue. IMO if the top card is getting too hot for your liking, then try 16/8 and see if the performance is the same. I'm sure that even if there is a performance drop, it won't really matter. SLI 680s is stupid fast. I hope you have a multi-monitor setup to use all that juice!

Also, depends on the model of 680.

Assuming no extra slots between cards, a lot of cards will only have about 1/8" of space to 1/4". That may not make it too hot, but it will make the fan run fast enough to make it loud.

Watercooling is the only way to properly cool in that type of config,imo.

Reference cooler will have a harder time of it than an aftermarket cooler. Too bad they got rid of the air holes in the PCB that some 500 models had.

But I mean it really depends on the fan profiles. The top card will probably get 10C hotter, but that's still probably under 80C which is totally safe.

Also, easy to make a spacer to stick in there. The top card will be drooping down, so there's room to lift it up.

And finally, a fan shroud to direct the intake air right at the card can help. Or use an Air Penetrator (Silverstone).

Regardless, the option of 16/8 is there if the temps or noise really is an issue, and it will probably perform admirably in that config as well.