In April I purchased two AMD HD 6850s and I've got them running in crossfire mode, after reading plenty of reviews I thought these cards had great scaling, but it seems that on almost every game I run I get negative scaling or a tiny performance increase.
Here are some examples:
F1 2010 in Crossfire - 30 to 45FPS
F1 2010 W/O Crossfire - 35 to 55FPS
Thanks for your replies, I'll try version 11.2 3 and 4 when I get home later and I'll also check the temperatures when I get home, I used to have Crysis 2 working much better than it does now, it used to average at around 80 - 110 fps, but then it just changed.
Crossfire has some significant CPU overhead, always has though they seem to be better about it now. If your CPU is the limiting factor in games then crossfire actually can lower the FPS since in addition to your CPU not being fast enough to provide one card with information, it needs to take cycles to divide up the work between the cards. You can hardly blame the cards for that.
What's the rest of your system? Did you re-install the drivers and make sure that the crossfire bridge is properly inserted?
Have you tried a driver uninstall and driver sweep before reinstallation?
Have you double and triple checked the the cards are both full inserted in the motherboard?
What motherboard do you own?
Have you checked what GPUZ says?
Are there any errors in the Crossfire tab of CCC?
1) Haven't Yet, what program should I use to ensure a full driver sweep?
2) Both cards are most definitely, positively, affirmatively in place
3) I have an ASRock M3A770DE, Not great I know, but isnt that bad
4) GPU Z says that crossfire is enabled with 2 GPUS
5) There are no errors in the Crossfire tab on Catalyst
Seems that CF is indeed enabled and should be working. One other thing, can you run MSI Afterburner and play one of those games? Just play for maybe 10 mins then go back and look at the graphs - make sure you have GPU usage and the core/mem clocks enabled at the least (and it's a good idea to make the graphs very big so they record and display more data). I'm wondering if the 2nd card isn't getting usage.
Oh right and which 6850s do you have, which model?
Older drivers shouldn't be better than 11.5 but sometimes you can be unlucky.
One other thing to try is to use each card on it's own in the primary slot and make sure that they each work individually.
Okay, I've got a fresh install of my Display drivers and CCC, this time, version 11.3, seems to run slightly smoother in crossfire. I took note of the GPUs usage, GPU 1 runs at around 40 - 50% and GPU 2 runs at 60-78%. So it's the first card not being utilised as much, a bit weird.
Ah, interesting. They should be nearly identical to eachother. Are they different models of 6850? And have you tried swapping out which one is on top?
Also, just to clarify something, the best method for reinstalling drivers is:
-uninstall CAP (add/remove programs)
-uninstall drivers (add/remove programs)
-run driver sweeper and remove all ATI display drivers
-reboot. resolution should be ultra low (800x600)
-install new drivers
They are the exact same model, there the Gigabyte OC versions. Havent swapped them around yet, will do it tomorrow as its midnight now. Thats pretty much how I installed the drivers, except I couldnt use driversweeper because I couldnt download it from Guru3D and the download I found elsewhere contains the program but doesnt work.
Just tested Crysis 2 for the first time after getting the older drivers and it runs at about 110FPS on the same mission where I was getting about 50FPS previously, and also I no longer get terrible lag when V-Sync is off and no black shadow in the middle of the screen on max settings.