Need some advice on Crossfire Config

[DisturbedJim83]

I currently have a single Powercolor PCS+OC R9 290 and want to add a second R9 290 preferably a second Powercolor PCS+OC R9 290 if I was to put 2 of these in the x16 and x8 slots of my Asus Maximus VI Formula there will be about 3mm of clearance between the backplate of the card in the x8 slot and the fans of the card running in the x16 slot.

My question is will 3mm of space be enough for the card in the x16 slot to breathe ? I have seen rigs at CES and E3 where 2 cards are practically touching and they seem to be ok but a nagging voice tells me its not advisable.

Next to getting full waterblocks for 2 Powercolor PCS+OC R9 290's the only option I can think of is getting something like a Asus Direct CU II R9 290 with a slimmer 2 slot cooler instead of my Powercolor's 2.5slot cooler putting the slimer card in the x16 slot and my Powercolor card in the x8 slot.

I had seen suggestions elsewhere about just buying a second Powercolor PCS+OC R9 290 putting 1 in the x16 slot and one in the x4 slot(slot 3) will this affect performance since both cards will be reduced to x4 speed ?

Any other ideas or suggestions would be appreciated as I'll be ordering a second GPU on July 18th

 

[Excalabur50]

It would be safest to put it in the 4x slot so that it does breathe better and it wont affect performance that much, 3mm of space just isn't enough space for air to penetrate and you don't want to kill your new card

 

[DisturbedJim83]

It would be safest to put it in the 4x slot so that it does breathe better and it wont affect performance that much, 3mm of space just isn't enough space for air to penetrate and you don't want to kill your new card

Thanks for the reply as I've been getting conflicting reports JJ from Asus was saying it would be ok though he advised a more aggressive fan profile on the GPU's and additional fans like the one's mounted to my Switch 810's HD Cages blowing air between the cards might make it feasible.

That being said putting one in the x4 slot and the other in the x16 slot would make more sense till i can afford a custom water loop for them both as that looks to cost around £600 which seems rather steep

 

[Excalabur50]

As you can see I also have an 810 and my cards have approx 20mm spacing and I direct my fans to them, so if you can get that good spacing the cards will stay reasonably cool

 

[DisturbedJim83]

As you can see I also have an 810 and my cards have approx 20mm spacing and I direct my fans to them, so if you can get that good spacing the cards will stay reasonably cool

Ok can always try it I guess my Powercolor Card has not gone above 71C under full load on its own,If I have trouble sourcing a second PCS+OC R9 290 would I be better of getting on of the Asus DC II 290's putting one of those in the x16 slot with my PCS+OC R9 290 in the x8 slot should give me about 15-20mm of cooling I think ?

 

[Excalabur50]

That should work but if you can you are better off trying to have matching cards

 

[WYP]

It always looks nicer to have matching cards but non matching cards, provided they are both 290s off-course.

Using the 4x slot will give a small bottlekneck, provided it is a PCI-E 3.0 lane.