EDIT: I got an answer in the Crossfire forum. The x4 slot is bottlenecking my system. : (
I already asked this in the AMD Crossfire forum as well, but it can't hurt to ask some more people.
I just bought and installed a second HD5770 in my computer today, and I've been trying to get it to work well.
My setup is as follows:
Intel Core i5 750
2x HD5770 (One is Sapphire Vapor-X, I forget what the other is)
Windows 7 x64
4 GB of RAM
ASRock H55M motherboard w/ most recent BIOS (2.20)
Catalyst Control Center 10.12a, I also tried with 10.9
I'm running World of Warcraft at 1680 x 1050, maximum settings other than 4x AA.
I am getting significantly lower FPS with CrossfireX on (~27 in Stormwind versus ~35 with only one GPU) in World of Warcraft. However, in 3DMark 11 I got on average double the framerate with CrossfireX turned on. In spite of this, I got the same score in 3DMark 11 either way, and it reported that I did not have two GPUs (?).
My motherboard's PCI-e slots are x16 and x4.
What information should I provide to make my problem more clear (and what programs I should be using to obtain that data)? What solution should I try? I have tried searching but I cannot find a solution, so I'm sorry for posting this but I honestly have spent hours searching through this forum and trying to find a solution that works for my situation.
I also notice that my computer seems to run a little strangely with CrossfireX on. Regular tasks like opening windows/etc. seem to cause unusual pauses. It's not huge but it's noticeable.
And before anyone says WoW doesn't benefit from multi-GPU, it seems like many people are finding they are getting nice performance benefits from Crossfire or SLI, so I don't see why I can't as well... T-T
I have used both cards by themselves and they both work perfectly.
In GPU-Z it reports Crossfire: disabled on one GPU and enabled (2 GPUs) on the other. I'm not sure if that's normal, but I figured it can't hurt to mention it.
I don't know where you've read,but WoW doesn't benefit from CF.
Try some other games(especially FPS tittles)and you should see a great boost in performance.
SC2 is pretty much like WoW,it doesn't benefit from SLI/CF.With my 5970,I get higher FPS with CF enabled.