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Poor performance with 6850 crossfired

D

dakU7

Gawd
Joined
Jan 22, 2011
Messages
977
I recently bought 2 6850s along with my new SB system, and I noticed earlier that i'm getting poor performance compared to benchmarks floating the net, so i downloaded Unigine and ran some tests.

Crossfire:

crossfire2.jpg


I benched each card on both x16 and x4 lanes, and the results were abit odd;

First card on x16 lane:

secondcard16x.jpg


I forgot to save the results for the second card, but the results are pretty much the same give or take 1%

And first card on X4 lane:

secondcard4x.jpg


Again, same results for the second card +/- 1%.
I'm pretty confident it's not the cards that are faulty but this makes no sense, shouldn't they perform better when placed on the 16x lane? is this a driver issue? or maybe the motherboard?
 
What are all of your specs? You're first bench is what you should get with a single 6850 that is slightly overclocked.. Which drivers? Try removing and going down a version. Do a complete uninstall of Ati install manager and retry. Got pics of relevant CCC settings?
 
Valset said:
no, not really. go read this http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4/

as for crossfire performance what game is it your having an issue with?
Click to expand...

Just about any game, on BC2 i even get lower performance with crossfire enabled than when it's disabled.

That article isn't related to the problem i'm having, i'm aware of the performance impact when using the x16/x4 lanes, and i know it shouldn't affect crossfire more than 5%.
Each of the cards runs slower on the X16, i'm actually getting better scores on Unigine, and better FPS on games when running a single card on the x4 lane. Shouldn't the PCIE X4 perform worse than the X16?

TomGreen321 said:
What are all of your specs? You're first bench is what you should get with a single 6850 that is slightly overclocked.. Which drivers? Try removing and going down a version. Do a complete uninstall of Ati install manager and retry. Got pics of relevant CCC settings?
Click to expand...

As for my rig, i'm using 2500K @ 4.4 with P8P67, 4GB and 750modXstreme.
I tried every driver from 10.10e through 11.1, i uninstalled and removed the remaining files with driver sweeper, I also made sure the settings in CCC are set to default.

Thanks, and sorry for my english :)
 
Hmm does look odd and a bit low. Stock my single 6850 in my old Ph II 940 rig does about 31FPS in Heaven v2.1 default. @ 945|1150 it does 36.6FPS.



That was done with the official 10.10 driver a bit ago. Mobo is an old Foxconn A7DA-S (790GX).
 
10.10 may be the best driver for Heaven v2.1. I'm going to drop my 6850 in my Intel rig and try it on that platform with the official 11.1s. BRB.
 
LMAO. The 6850 @ 945|1150 is slower in my well overclocked Intel rig with the official 11.1s.



If all you want to do is bench Heaven v2.1 try the official 10.10s, not any hotfix 10.10s they are slower.
 
Thanks alot! it's still much faster than what my cards are getting, your card is actually close to the results i'm getting with CF enabled.
 
I've got a decent OC on the card. The 6850 @ stock in my Intel rig does just over 28FPS with 11.1.

Try the official 10.10s if you want to experiment with Heaven. Also "warm" the bench. Or that is, let it loop one time before you press benchmark.

I'm going to go play Mass Effect 2 with MLAA applied since I've got the card installed. WTF.

Best wishes.
 
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Have you run it with your processor at stock? What kind of temps are you seeing? Try running gpuz and have it run a log after running heaven. Check for low volts as well.

Newest chipset drivers? I would run HWmonitor or something and check for +12v fluctuations as well.
 
OK, few updates:

I downclocked the CPU to it's default clocks, temps are ~27c and 42c max core when running Unigine.

I ran 11.1 again with default settings, scores are pretty much the same as before:
Avg FPS - 51.2
Scores - 1289
Min FPS - 14.0
Max FPS - 121.8

Uninstalled 11.1 and ran driver sweeper, then installed 10.10. Scores are somewhat better with 10.10, but still not close to what i should be getting;

CF1010.jpg


GPUs are running at stock clocks, temps are 34c at idle, 70c when running Unigine. max volt is 1.15v, min is 0.95v.
I updated everything, including chipset drivers. I seriously don't know what could be the problem. I'm leaning towards a defective motherboard, what do you guys think?

EDIT: tried BC2 again, i still get messed up FPS (avg is 22~ everything maxed) when enabling CF.
 
22FPS in BC2 with Crossfire enabled sounds like a missing or broken driver profile which would result in negative scaling.

Try it with Crossfire Off. If your FPS >improves<, that may be the problem.

In that case, uninstall the CAP. Uninstall your driver. Restart.

Install your driver. Restart. Install your CAP and make sure Crossfire is enabled. Restart and try BC2. Also make sure your AA in the CCC is set to standard and not to edge under AA filter.

If you're still getting low FPS, I'm not sure what to say. Again, It sounds like negative scaling to me because of a missing or borked Crossfire driver/app profile. 6850 Crossfire should be pushing 70 some FPS in BC2.

http://www.guru3d.com/article/radeon-hd-6850-6870-crossfirex-review/7

Best wishes.
 
Yes. When i disable CF the FPS jumps back to ~40 avg.
I tried 2 CAPs already, but i'll try it again in that order.

What about the issue i'm having with the x16 lane? do you think it has something to do with the motherboard?

Edit: didn't worked.
 
Last edited:
Well you have me stumped :(

You're definitely experiencing negative scaling in BC2. 52FPS in Heaven v2.1 @ 1920x default means 6850 Crossfire is working in that bench. I'm not sure why it's broken in BC2 for you. The last things I can think of would be to try 11.1a with the latest CAP if you haven't done that. You could also try toying with Radeon Pro.

http://support.amd.com/us/kbarticles/Pages/AMDCatalyst111aHotfix.aspx

http://www.radeonpro.info/en-US/

You may want to ask around Rage3d as well. Some beta testers hang around there.

http://www.rage3d.com/board/forumdisplay.php?f=59

Wish I could be more helpful.
 
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Lots of reported cases of negative scaling with 6850s in BC2. Try 11.1a, that's supposed to fix it.
 
Ok guys, thanks a lot! I'll give rage3d a shot.
Just one more question tho, what about the fact that each card runs slower on x16 lane? Is that normal?
 
So that's the reason i'm getting slower performance on the x16 lane compared to the x4?
 
Just ran the test, i'm getting 6GB+ on both sides. I also updated to the latest drivers, bc2 is still messed up :confused:
 
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