Flogging a dead horse - Microstuttering in Crossfire

Hi All,

I've recently added another HD 5970 to my setup:

CPU: i5-3570K @ 4.5Ghz
RAM: 4x2GB G.Skill Ripjaws 1600
PSU: 950W Corsair
GPU: 2xHD 5970
Drivers: 12.10

I'm experiencing what I suppose is micro-stuttering, i.e. FRAPS gives the fps as very high, but it feels like 20fps.

Now, I know micro-stuttering is pretty much an unsolved problem for most people, and these cards are getting old quickly, but here's what I simply cannot understand:

Some games (Rage, Bioshock 1, Far Cry 2) run as smooth as you can imagine at very high fps (except obviously Rage, as it has a 60fps limit built in, but with XF enabled, it never dips). I'm checking the GPU load with MSI Afterburner, and in all these games the load on all 4 GPUs seem to react dynamically to how intense the graphics are at that part of the game. It's usually also quite high (anything from 70% - 99% on all GPUs).

Some other games (Far Cry 3) also has a high framerate (60 - 180) but it feels like 20fps which is absolutely unplayable. The thing is, the GPUs all have a load that stays at +-40% no matter what. I've messed around with all the settings in CCC, alt-tabbing out of the game and alt-tabbing back in, changing the game settings etc. Now here's the ridiculous bit: Every now and then after messing with some settings, it's like the cards really kick in and the load goes up to 70 - 100% and the game runs smooth as can be (also it doesn't crash constantly). Unfortunately there is no consistency here. I've even written down all my steps and tried it again, but it doesn't yield the same results.

Even stranger, after the first problems I had with FC3, Rage now just crashes to desktop on launch if XF is enabled. If it's disabled it doesn't crash, but now I'm getting micro-stuttering on the single card setup as well.

So this is the riddle I'm trying to solve: Empirically, it seems that there is a way to get rid of micro-stutter as I've seen it with my own eyes. I just cannot figure out exactly how.

I've installed/uninstalled drivers (including driver sweep after) 12.7, 12.8, 12.10 and 12.11 beta, I've closed all logging programs (FRAPS/MSI Afterburner etc.) but it just seems everything's busted right now. I'm at my wits' end here. Any help would be greatly appreciated.

Thanks!