6850 Crossfire still doesn't work

tjcoops

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A few months ago I had a thread on here because I found that my 6850s in Crofssfire were negative scaling on just about everything. Back then we came to the conclusion that my processor, the AMD Athlon II X4 635 was to blame because it wasn't powerful enough to feed both of the cards.
However, I recently helped a friend of mine rebuild his computer and in return he gave me some money and his old processor. The processor is an AMD Phenom II 550BE. It successfully unlocks to a quad core and I currently run it at 3.6GHz. It is significantly more powerful than my old Athlon. However I'm disappointed to find that the result is the same, negative scaling on every game. It only seems to work well on the Heaven benchmark.

I have tried everything I can think of, just yesterday I used Atiman Uninstaller to rid my system of EVERYTHING to do with ATI & AMD and reinstalled the latest driver and cap, all to no avail. I'm getting tired of it not working and I'm really in desperate need of help.

Thank You,
Tristan

CPU - AMD Phenom 550BE UNLOCKED and OCed to 3.6GHz
MOBO - ASRock M3A770DE
Graphics - 2x Gigsbyte Radeon HD6850
PSU - Coolermaster 650w
RAM - 2x 2GB Kingston HyperX 1333MHz
 

4745454b

Titan
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I'm going to go with board, perhaps PSU. Your board does 16x/4x CF, so you basically have two cards in 4x mode. CF should work, but not very well.

Which CM PSU? They have some duds so perhaps your cards don't have enough power? CF bridge is on? Enabled in drivers? Testing with games that support CF?
 

hella-d

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I Know For A Fact That Is Not Your CPU, A Friend Of Mine As An Athlon 64 X2 6400+ @ 3.2GHz And 2 GT275s SLI And Is Having No Problems What So Ever, The Problem Is That You Shoud Never Run Mutiple Cards Below x8 PCI-E
 

tjcoops

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Sorry for not making it more clear. I run games at 1920x1080. The games I have tested include F1 2011, Crysis 2, Battlefield 3 and DiRT 3.

On F1 2011 with the benchmark I get:
Avg - 53FPS (No Crossfire)
Avg - 47FPS (With Crossfire)

On Crysis 2 I get:
Around 50 - 60FPS (No Crossfire)
Around 15-30 (With Crossfire)

Battlefield 3:
Around 50 - 65FPS (No Crossfire, Everything Medium)
Around 20 - 30FPS (With Crossfire, Everything Medium)
 

tjcoops

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Really! That's awesome. I knew there was a loss of performance when running cards at x8 and x4 but I always thought it would only be 5-10%. Problem is, I know nobody who has dual 16x or 8x motherboard so I can't test my graphics cards on another motherboard.
 

jjtober1

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I've read that the drop off for using one of the latest cards in a 4x slot is like 25%, but I doubt it would be that high for a 6850.

I would use MSI Afterburner to see what your GPU's are actually doing. Maybe you could try a fresh install, I just switched an Nvidia for an AMD card and the driver would not load right no matter what I did. I did a fresh install it worked properly, AMD drivers seem to be finicky sometimes.

I have never heard of actually getting negative scaling from a 4x slot.
 

tjcoops

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I used Atiman Uninstaller to rid my system of graphics drivers and installed the latest ones. I did this twice and crossfire still doesn't scale properly. I will have a look at GPU utilisation at some point tonight and get back to you.
 

tjcoops

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Okay, I've done some tests on the GPU Utilisation in Crossfire. When playing F1 2011 my primary card runs at about 50% and my secondary runs at about 80-90%. The processor was running between 65 and 75%.

Maybe this indicates that the secondary card is using almost all the bandwidth it can get from the PCIE x4 slot and the primary card has to slow down to stay in sync with the slower card?

I doubt I'm 100% correct but that seems quite likely?

Thanks
 

lolzxdrofl

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Get GPU-Z if it tells ur its enabled then u are also on crossfire x16 x4 can be a huge significance, because if its x16 x4 its almost useless to have two cards one's running at x16 which means for crysis 2 50-60 fps like u said, but the 2nd is only x4 so it makes it considerably weaker
x16x16= 93-97% efficiency
x8x8= 83-91% efficiency
x16x4=71-80% efficiency
and these are for gpu supportive games some might even go below 50% but crysis 2 is not one of those games.

although the FPS shown here means that the FPS still should go up by quite a bit, it could be a problem where one of you're cards is defective, u should try switching around the cards and if it still 50-60 fps with each individual cards it's possible you're motherboard is malfunctioning and it's hurting another video cards fps or something and only the x16 slot works, u should try getting a new mobo or burrow one and see the results.
i have the same 6850 crossfire and cpu
i also have the Gigabyte FXa-ud3 which has x16x16 for about 150$.
 

amirp

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I am not sure but could 2 x 2gb 1333 ram pose as a bottleneck for a crossfire situation?

also are you installing BOTH the full Catalyst Software Suite AND the seperate link for the ATI Catalyst Application Profiles on the AMD driver page?

Even if you are running at 4x it shouldn't really decrease performance....
 

tjcoops

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Yep, I've got both the latest drivers and cap. I don't think the ram should act as a bottleneck, both the speed and capacity is pretty good
 

amirp

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I suggest trying the following single card experiments:
try each of the Single Cards in each of your slots, so Card A in the 16x slot and 4x slot, then Card B in the 16x slot and the 4x slot (so 4 tests). Run a consistent benchmark like unigine, or if you have crysis use the benchmark tool, or games with benchmark tool include: arkham asylum, res evil, far cry 2, metro2033, dirt 2 and 3

This will let you compare Card A to Card B AND the two PCI-E Slots to each other.

This would conclude whether for example one card is defective, or if one of your slots is either defective or the 4x slot is actually really slowing you down.
 

amirp

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Lol true... but I repeat it for clarification and the fact that he has to do those tests I (we) mentioned to rule out a bunch of critical stuff
 

tjcoops

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I've done the tests. I get pretty much the same results on both cards and on both the x16 and x4 slots. The x4 slot results in about a 1FPS decrease, that's it. I can't think of anything else that could be causing the problem.
 

Djentleman

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I hate to be like this... but, i think it's still your CPU.

The 550BE is a weak cpu. You may have it overclocked, but your problem is cache. You need cache to have better transfer between your GPU; CPU; and ram.

I'm pretty sure this is what is messing you up. It may be able to run two 275s - but the 275 is not a processor hungry "modern" card.

The 6850 is also known for being risky in crossfire. I would suggest a new CPU and MOBO. This will most likely solve your problem!
 

tjcoops

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It's unlocked to a quad core as well however, which means the performance right now is closer to a Phenom II X4 965 than anything else (it also has the same cache) and from what I've seen a X4 965 is perfectly capable of running the 6850s in crossfire.

 

4745454b

Titan
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I don't think its a CPU issue. If it can do two 275s, then the 6850 isn't a problem either seeing as the GTX275/280/460 and 6850 all have very similar performance. Difference is in power use and DX levels. Not sure what you mean by "risky" so I'll ignore that.

Any update on the PSU? Try other CF bridges yet? Update drivers or CAP? (the application profile things.)
 

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