What kind of performance degradation am I looking at by running a 6850 in a X8 slot?

[JM Popaleetus]

As you can see by my sig, I have two 6850s that I am running in Crossfire. Unfortunately, the way my motherboard has its x16 slots, one is suffocating the other. One loads out at 60C while the suffocated one loads out at 100C. Even idle has a 10-15C difference.

Now unless there is an aftermarket cooler that can fix this, the best way would be to move the second card down a slot. Unfortunately by doing this the second card would end up in a x8 slot and not a full x16 slot.

What kind of (if any) performance degradation am I looking at?

 

[happy medium]

None, worst case 2%, you should be fine.

 

[JM Popaleetus]

Does the AT community agree with this?

http://www.hardocp.com/article/2010/08/16/sli_cfx_pcie_bandwidth_perf_x16x16_vs_x16x8/6

You can find slight framerate differences between x16/x16 and x16/x8 SLI and CrossFireX video card configurations if you go looking for them while pushing games to super high end resolutions and quality settings, but nothing that negatively impacts a real world gaming experience. If you are wanting to use SLI or CrossFireX on that motherboard that does not support x16/x16 PCIe lanes, have no fear. If you do have a x16/x16 motherboard and want to space those hot video cards out a bit to let those breath a bit easier, well have at it.

 

[JM Popaleetus]

None, worst case 2%, you should be fine.

HardOCP noticed at max a 3FPS difference. Cooling down my cards by 10-30C I feel is much more worth it.

 

[Powermoloch]

my mobo goes 16x/4x

And comparing with other benchmarks that use 16x/16x lanes. Hardly of a difference at all

unfortunately with my config, my top gpu is a few degrees hotter than the one below.

 

[jacktesterson]

Do it, you will NOT NOTICE a difference.

Too many on paper geeks lol

 

[JM Popaleetus]

Do it, you will NOT NOTICE a difference.

Too many on paper geeks lol

I actually went a step further and went x8/x8. I now have three expansion slots open that won't interfere with the GPUs as well as the max possible space between the GPUs I can have.

Win. Win. Win.

Thank you for your help again guys.

 

[JM Popaleetus]

Well the good news is that the temps are down 10C at idle on both. That said, one card is still 10C hotter (instead of 50C/40C it's now 40C/30C). When I go home next I'll probably repaste that top card.

Unless this of course is a common trait with crossfire?

 

[taltamir]

it might be your case's structure/airflow... it might be chip binning (one of them might have a higher power consuming chip despite identical name and design)... it might be that one has lower quality application of thermal paste.
Couldn't hurt to repaste it unless the manufacturer voids your warranty for it, or unless you break it in the process.

 

[Triggaaar]

I actually went a step further and went x8/x8. I now have three expansion slots open that won't interfere with the GPUs as well as the max possible space between the GPUs I can have.

Win. Win. Win.

Ooo, interesting...

I have an Asus p6x58d-e, with 3 slots, which can run either 16, 16, 1 or 16, 8, 8. Does that mean I can use the 1st and 3rd slot (without a noticeable difference), to allow me to keep my middle PCI slot?

Thanks

 

[digitaldurandal]

100c isn't terrible for a gpu. However if you have an x8 slot i would go ahead and move the card.

 

[JM Popaleetus]

Ooo, interesting...

I have an Asus p6x58d-e, with 3 slots, which can run either 16, 16, 1 or 16, 8, 8. Does that mean I can use the 1st and 3rd slot (without a noticeable difference), to allow me to keep my middle PCI slot?

Thanks

Yes.

 

[Jdawg84]

 

[Rezist]

100C IMO is pretty damn hot, I'd like to see any GPU I own not break 85C.

 

[jacktesterson]

I've got 2 GTX 470s only one spot apart and the sparkle card (the top card) is always 10 degrees hotter, and it's a non reference cooling card. I've got excellent cooling with 4 120mm fans and 2 240mm fans.

Mine run idle in 30's/40's and load in 70's


Anyways glad it helped but 100 is way to hot IMO.

I think it's fairly normal for 1 card to be warmer in cf or SLI setups

 

[ModestGamer]

waterblocks and a small liquid cooling system.

 

[JM Popaleetus]

Mine run idle in 30's/40's and load in 70's

Good to hear that differnences in temp is not uncommon. I'm down to a ~5C difference now.

Furthermore, my idles are in the 30-40C range with load peaking at 80C. Just where I want it :thumbsup:.

waterblocks and a small liquid cooling system.

Too expensive and unreasonable for my needs.

 

[ModestGamer]

Good to hear that differnences in temp is not uncommon. I'm down to a ~5C difference now.

Furthermore, my idles are in the 30-40C range with load peaking at 80C. Just where I want it :thumbsup:.

Too expensive and unreasonable for my needs.

3 lbs of copper a few barbs and a mill could fix the exspense part. Waterblocks are fiarly exspensive but very easy to make.

 

[Modular]

3 lbs of copper a few barbs and a mill could fix the exspense part. Waterblocks are fiarly exspensive but very easy to make.

I have access to none of those things, and I'd bet that most people don't. Also, isn't copper pretty expensive to buy?

 

[dust]

Same issue here, one card is always hotter by 12-15c than the other one, but I don't think it is related to the cf, one of the cards is simply running hotter regardless where I put it, even if I run it alone.

100c seems A LOT to me, thermal paste needs to be changed probably.

 

[zerocool84]

Does x8/x8 not make a difference either?

 

[tweakboy]

Wow good informational thread. so the consensus is ,, it DONT matter either way.. g1

 

[Jdawg84]

Does x8/x8 not make a difference either?

Less then .5 fps

 

[JM Popaleetus]

Does x8/x8 not make a difference either?

Unless you're running a setup with 5760x1200 resolution....No.