Crossfire Hd 7950 worse than single hd 7950 when playing games

Stephen Whitson-1324651 · Oct 22, 2013

Hi I recently purchased a second hd 7950 to crossfire one is vapor x and the it here is a vtx3d I'm running windows 8.1 with the latest drivers. When I run games eg tombraider 20fps, metro last light 25 fps, far cry 3 4 fps. The load of both gpus are only between 30 to 40% each. I did manage to get 1400 score on 3d mark. I have disabled upls using a free tool. I am using msi afterburner to monitor Gpu usage.
Motherboard - p8z77– lx
Psu - 750 watt crossair
Ram. - 8 gig

Any help from someone who knows what the are talking about would be appreciated. Thanks

expl0itfinder · Oct 22, 2013

Those numbers are extremely low...for 3DMark 11, this is what you would be seeing:
http://www.legitreviews.com/amd-radeon-hd-7950-3gb-crossfire-review_1853/9

Make sure crossfire is enabled in the drivers, and reseat both the cards. What CPU do you have?

expl0itfinder · Oct 22, 2013

Actually, I just checked out that motherboard. It does not support multi-GPU configurations, as the second PCIe slot is only PCIe 2.0 4x.

lowriderflow · Oct 22, 2013

i'm going to guess since 8.1 it's pretty new, they havent' quite gotten there on the crossfire drivers.

welcome to the world of AMD crossfire. it's horrible.

i had this issue on windows 7 with some of the beta drivers. some worked fine, others were horrible.

try the prior version of drivers.

install radeonpro as well

RobCrezz · Oct 22, 2013

expl0itfinder :

It says on the website it supports crossfire.

What CPU do you have op?

expl0itfinder · Oct 22, 2013

lowriderflow :

RobCrezz :

Let me rephrase that. The second GPU will be bottlenecked to the point of holding back the other. Since the idea of crossfire is to share frame rendering between 2 (or more) GPU's to increase performance, it does not apply to this motherboard. Now it does support crossfire of extremely old cards, (4xxx series anyone?) but anything in the past 4-5 years will be bottlenecked.

RobCrezz · Oct 22, 2013

expl0itfinder :

lowriderflow :

RobCrezz :

Let me rephrase that. The second GPU will be bottlenecked to the point of holding back the other. Since the idea of crossfire is to share frame rendering between 2 (or more) GPU's to increase performance, it does not apply to this motherboard. Now it does support crossfire of extremely old cards, (4xxx series anyone?) but anything in the past 4-5 years will be bottlenecked.

Actually I think you'll find, even a 4x pcie 2.0 slot barely causes a bottleneck.

expl0itfinder · Oct 22, 2013

PCIe 2.0 4x has a 2GB/s bandwidth limit. Modern PCIe 3.0 x4 has a 4GB/s bandwidth limit. The 7950 bottlenecks at PCIe 2.0 8x, which is also 4GB/s. So by cutting it to 2GB/s, you effectively halve the performance in the majority of applications.

Kari · Oct 22, 2013

RobCrezz :

it will, a little bit
136 vs 163fps, same as going with a fx-8150 instead of the 3770k lol

http://www.anandtech.com/show/7189/choosing-a-gaming-cpu-september-2013/7

and in other games it doesnt really have any effect

WarWolverineWarrior · Oct 22, 2013

yeah you need 2x8 lanes PCIe 2.0 both to run 2 AMD GPUs

I got the p8z77– LK just for that reason, or else I would've went with LX
http://www.asus.com/Motherboards/P8Z77V_LK/#specifications

nikoli707 · Oct 22, 2013

another common yet monster reason a single fast gpu is vastly better than sli/cf

Stephen Whitson-1324651 · Oct 22, 2013

expl0itfinder :

I was worried you would say this, I read lots of threads and no one had mentioned to watch out for this. I'm really angry as I spent a lot money to go crossfire and they don't tell you this stuff on the Asus website. Yeah crossfire compatible my arse, I guess I'll be selling my other card.

WarWolverineWarrior · Oct 22, 2013

Stephen Whitson-1324651 :

Sell your MOBO and get LK
http://pcpartpicker.com/part/asus-motherboard-p8z77vlk

expl0itfinder · Oct 22, 2013

Stephen Whitson-1324651 :

Sorry man. But hey, take it as a learning experience. Honestly, there isn't a need to upgrade the motherboard, or even the graphics card for that matter. The 7950 is a beast, especially at 1080p or lower. I would wait for next year's generation of cards, or until the R9 series comes down in price, and then just grab a single, more powerful graphics card.

Kari · Oct 23, 2013

did every one just plain ingnored those two charts i posted??

expl0itfinder · Oct 23, 2013

Kari :

Those charts are not relevant. Almost all of the benchmarks were in 8x/8x or 16x/8x. The only few that were with 16x/4x were with low end processors, which would bottleneck dual 7970s anyway. We do not know the OP's processor, however.

Kari · Oct 23, 2013

expl0itfinder :

so a 3770k is a low end cpu, ok

expl0itfinder · Oct 23, 2013

I said almost all. They benched with one relevant CPU. Either way, it's safe to say that isn't the issue. The symptoms are quite clear. If it were a CPU bottleneck, then you would see spikes in FPS, and you would still get a pretty good 3Dmark score. His situation is a telltale sign of a PCIe limitation, or the motherboard's inability to support dual GPU's. I make this claim primarily because he/she actually saw performance DECREASES when adding another card, where if it were properly supported but not set up correctly, the performance would remain the same as with a single GPU.

Kari · Oct 23, 2013

expl0itfinder :

you said "The only few that were with 16x/4x were with low end processors, "
and the chart clearly has 3770K being run on a similar mobo as the op has, with one pcie 3.0 16x slot and another pcie 2.0 4x slot and it is working quite well.

I'm more inclined to think there is some driver issues with crossfire and win 8.1...

expl0itfinder · Oct 23, 2013

Then let's test this theory. OP, download these drivers, and do a good ole reboot:

http://support.amd.com/en-us/download/desktop?os=Windows 8.1 - 64

If the issues persist, then it is a PCIe issue. If you see a humongous performance increase, then I stand corrected.

Kari · Oct 23, 2013

There's no driver available at the page you linked?
and secondly if it is a driver issue there might not be a fix available just yet... amd tends to be somewhat slow fixing things lol

expl0itfinder · Oct 23, 2013

Sure there is. "Catalyst Software Suite" includes the driver. And AMD has been absolutely fantastic with their drivers so far...the Windows 8.1 driver was available Oct. 18th, and Windows 8.1 was released on the 17th. One day later. The only long lasting driver issue that AMD has had was the frame time variance for multi-GPU configurations.

nikoli707 · Oct 24, 2013

13.11 has been out so definitely skip that 13.9 whql crap... i haven't used a whql in years because there is almost always a better beta out a few days after a whql release. also... a manual uninstall is the only way to upgrade drivers for your amd/nvidia card... so make sure to always do that.

Mlim666 · Oct 24, 2013

Did you check you "power options" I know that Crossfire FAILS to even work when my power option is set to "power saver" (I change from Performance to power saver when downloading.)

Kari · Oct 24, 2013

expl0itfinder :

There's nothing availlable to download on that page, all I see are section headers but it's all empty beneath them. Nothing there to click on...

Crossfire Hd 7950 worse than single hd 7950 when playing games

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