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PCI-e config = very hot cards!

ev0styLe

ev0styLe

ev0styLe

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Joined
7 Dec 2008
Posts
144
Location
Brighton
Hello guys,

I have just bought myself a couple 6850's for Crossfire. Problem is, the PCI-e config on my motherboard means my cards are pretty much on top of each other, allowing very little space between them. Below is a pic:

http://images.highspeedbackbone.net/skuimages/large/A455-2868-Main-JH.jpg
No hotlinking pictures please.

I have myself an Antec 1200, in which I have fitted a 120mm fan on the side panel to pull hot air out, but I'm still reaching 90 degrees in games. There is a soundcard installed on the third PCI-e slot (white) which covers half of my second GPU's fan, and my first GPU's fan is completely covered by my second GPU. My question is, what would be the best way to cool these cards? If any?
 
I'm not sure the performance hit for running the card in the 4x slot will be more than single digit percentage. Probably worth it for the better cooling?
 
Yeah, with those carrds, it's worth trying the x4 slot. You should see only minor differences. I remember an article sometime back which compared using the different slots. x8 was barely noticable below x16; x4 varied from a few percent to 10% (fort the high end card they used), and x1 was a fairly drastic drop as you'd expect.

Definitely worth trying.
 
MeMeMeMe said:
Yeah, with those carrds, it's worth trying the x4 slot. You should see only minor differences. I remember an article sometime back which compared using the different slots. x8 was barely noticable below x16; x4 varied from a few percent to 10% (fort the high end card they used), and x1 was a fairly drastic drop as you'd expect.

Definitely worth trying.
Click to expand...

The only CrossFire tests I've seen show an average reduction of ~10% going from x8/x8 to x16/x4 using HD 6950's.

The maximum reduction was 26%.

Going from x16/x16 the reduction might be a little more, using HD 6850's might make the reduction a little less.

Does CrossFire Work At x16/x4?
 
I had same problem with 5870's on an Gigabyte EX58 board. Have since replaced the cards with a 7970, but a partial solution which seemed to work was to wedge a piece of plastic between the 2 cards, to create a small gap.

I cut the ends of 4 cable ties and layered them on top of each other and wedged them between. Seemed to drop the temp of the top card by a good margin, where the both cards were idling at roughly the same temps (give or take 3or4 degrees) and loaded they were within 10 or so degrees of each other. It is indeed a very crude method, but it does work to an extent.
 
Use the spotcool behind my gtx 470's.

IMG_0032.jpg


Helps keep temps pretty even when gaming.
 
Surveyor said:
The only CrossFire tests I've seen show an average reduction of ~10% going from x8/x8 to x16/x4 using HD 6950's.

The maximum reduction was 26%.

Going from x16/x16 the reduction might be a little more, using HD 6850's might make the reduction a little less.

Does CrossFire Work At x16/x4?
Click to expand...

The interesting thing about those comparisons is that the 10% or less redeuction occurred in games where frames were lowest, and the 20%+ reduction occurred in games where the frames were very high - and where that loss would have little impact (probably).

Also that article is for high end cards; with the OPs 6850, I suspect the difference will be less - they dont need as much bandwidth. It would be interesting to find out if that's true, anyway.
 
My Crossfire bridge isn't long enough to test the difference in performance with my second card in the x4 lane but I have wedged a tooth pick inbetween my cards for the time being. This has dropped my temps by 10 degrees which will have to do for now. They definitely look awkwardly bent though, nobody likes a bent card ;)

I just hope it doesn't do any long term damage.
 
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