I have found a solution to my ridiculous stutter and GPU usage drop issue with the 7970 Matrix Platinums in crossfire I posted here:
http://forums.overclockers.co.uk/showthread.php?t=18496162
I originally managed to sort out BL2 but installing RadeonPro and setting Flip Queue Size 1. However, this didn’t solve BF3, Metro, Heaven or 3D Mark Firestrike. I tried everything Google was throwing at me apart from a complete OS rebuild.
In the end I finally found a solution….
Before:
I got rid of the 7970s (actually still trying to sell one in MM) and got a GTX 690!!
I have around the same FPS, some better, some worse but the difference is really in how smooth it is. It’s smoother now than it was with one 7970, I cannot explain fully how silky gaming is now. As another bonus, PhysX running on GPU, matters to some. So far I am VERY pleased with the GTX690 and I’m surprised at how well it overclocks and how quiet it is. I have the fan on 100% and it’s quieter than one 7970 Matrix Platinum @ 60%...
Even the little things like 3D Mark 2011 and Heaven, there were parts that used to jerk a couple of times at certain points naturally, regardless of what settings used or RadeonPro running, just thought it was the benchmark, those jerks are gone!
My whole experience with AMD Crossfire was terrible, with one card it was okay, minor issues to be honest, nothing that couldn’t be solved with yet another driver update here and there. But Crossfire? I am actually shocked at how bizarre it was. In reviews, here and other forums you will notice a lot of people experiencing no problems or some with minor issues that they “resolve”, and crossfire gets recommended all over the place. After my experience, I regret ever moving from nVidia and I can no longer recommend Crossfire as a valid option. However, I won’t blab about my experience and tell people not to go for AMD Crossfire, as there are many that have found it working fine for them. I’m just sharing my experience and conclusion.
Now I can put that behind me and sit for hours on end playing games, rather than tinker, tweak and pull my hair out. Yay!