No FPS gain at all from adding a second 7950 for crossfire.

Pavel Pokidaylo

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Just added a second 7950 to my computer. It's an Alienware Aurora with a Micro ATX motherboard, i7 920 CPU, and 8gigs of ram.

The top card is getting hotter than it did before but I guess that is to be expected. Especially with how close the cards are on this micro ATX motherboard. But why am I not seeing any kind of performance gain? I put in the crossfire Bridge and I enabled Crossfire in CCC and frame pacing is on.
 
Solution
What kind of air flow do you have in the current case?...number of fans etc...? If both cards are running 100% thats always good, but try and monitor CPU and gpu usage on those games where you feel that you are not getting any improvement.
What PSU do you have? What kind of frames are you getting? If you have vsync on you can't go any higher than your monitor's refresh rate which for most people is 60 fps. What CPU do you have, and check your CPU usage, if the CPU is maxed out then you are probably getting bottlenecked there.
 
Check that Vsync is off, both in the drivers and game/s.
What is the display/s resolution/s?
If you're using a single fairly small monitor (below 1080 rez) it's probable the system has run into a CPU bottleneck-The CPU simply cannot give two cards enough data for them to run at full speed.
The motherboard is, I think, PCI-E 1.0 which will shave a little off the GPU performance, download and run GPU-Z to see the PCI-E link revision and speed.
One point, the 7950 will downclock on idle and if you have a later PCI-E slot it may revert to an earlier revision (my 7950 will show PCI-E 1.0 at idle even though it's on a 2.0 MB), use the render test built into GPU-Z (it's to the left of the PCI-E info box), this'll wake the card up and kick it into full performance mode.
 

Pavel Pokidaylo

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I have an i7 920 and a 1080p monitor 24 inch. I put the original card in the bottom slot and the new card on the top slot and put on the crossfire bridge. Then I enabled Crossfire of course and frame pacing was turned on. I tried a few different games. Crysis 3, Metro LL, Far Cry 3, Hitman-Absolution, Tomb Raider.

First of all the temperature of the top GPU got to 95 degrees after only 5 minutes of Tomb Raider with max settings and 4SSAA. Tomb Raider was the only game that I think I saw a performance gain in because I turned on max settings and 4 SSAA and was around 60fps running around for about 5 minutes and then I saw the temp reach 95 degrees so I turned off the game. While it was on both GPUs were at or near 100% usage. I didn't check the CPU usage. The other games didn't seem to show any performance increase at all. I went to the same places in the same games with the same settings on and got the exact same FPS as I did with the one card.

Maybe the card is downclocking itself to try and prevent overheating. When I turn on max settings and high AA I can hear the cards working harder and the top card gets hot immediately. The fans were at 99%-100% when the card was this hot. This is an Alienware Aurora case. It's only about 16inch in height and uses a micro ATX motherboard. I thought the card would overheat because of the close proximity of the 2 cards. One is basically right on top of the other. But I was told that's how it is on all motherboards including ATX.

The guy at the computer store told me one thing we can do is put all my components in a different case and put 3 noctua fans to cool the cards. At this point I'm starting to think it's impossible to get a decent dual-gpu setup running. I mean the crazy high temps and not seeing any fps gain at all in most games is discouraging.

Do you think the card is downclocking itself due to the heat and that's why I'm not seeing much performance gain? Would using a different case and some good fans keep the temp down? I'm clueless =/
 

Pavel Pokidaylo

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About the Vsync it's the same with it on or off. If it were 60 fps I'd be happy. I'm seeing low fps in some games like Metro LL 21 fps, FarCry 3 25fps. This is the exact same FPS I had with just the one card.

Also the CPU is liquid cooled.
 
What kind of air flow do you have in the current case?...number of fans etc...? If both cards are running 100% thats always good, but try and monitor CPU and gpu usage on those games where you feel that you are not getting any improvement.
 
Solution

Pavel Pokidaylo

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I know it has one fan for PCI slots and one for the hard drive. Theres a liquid cooler for the CPU and a thing that sucks out the hot air I think. I just read that having the bottom card drive the monitor and the top card act as the secondary can help with temp?