JackNaylorPE :
Another anecdotal experience that is in complete contrast w/ reality. Upstairs I can hear games being played on the following:
Son No. 2 - Single 580
Son No. 3 - Twin 560 Ti's
Two 560 Ti's (Asus DCII TOP) for $400 outperform the single 580 (EVGA FTW) by 40% .... a mark which is echoed by dozens of published reviews.
Simple Rules of SLI / CF
1. No sense going that way if the rest of your system will bottleneck it.
2. Microstutter is NOT on issue with mid-range ==> high range cards ($200 and up).
3. No more than 2 cards in CF.
4. Power Supply must be beefy enough and must supply stable voltages (1% variation) if you want the highest overclocks.
5. SLI / CF options with mid range cards consistently have a lower cost per frame that the top tier single card solution.
actually microstutter IS an issue with high end cards, its just that normally the FPS is so high you dont notice it, or your using vsync which is like a frame rate cap which abolishes microstutter, so long as you dont dip below that cap. Also, Nvidia cards dont suffer such poor frame latency so microstutter is less noticeable. Also, a 3rd card in crossfire actually reduces microstutter significantly, toms had an article about this a while ago. I guess AMD decided when a third card waws present they needed some algorithm to sync the frames better from 3 cards, but you also dont see as much performance boost from the 3rd card.
I think in the OP's case:
1. CPU bottleneck in many games, the i3 aint enough to push those cards and keep the minimum frame rate up to avoid stuttering.
2. a possible wrong/corrupt installation, you should never see a decrease in FPS even if you are cpu bottlenecked just because crossfire is enabled. Maybe a motherboard issue also.
3. Some games do run worse with crossfire, this is not avoidable it is up to the game devs to fix or AMD to fix the driver.
4. if you want crossfire you need to be a tweaker, experiment with settings, and use aftermarket tools to help. If you want things to be straight forward with no issue, get a single card.
A while ago i upgraded my single 6850 to crossfire 6850's, it was only a month before i sold them due to microstutter/performance issues. A few games ran absolutely fine, i always saw an FPS increase over a single card, but some games the stuttering was all too obvious, even after playing with radeon pro fps caps and different crossfire methods. In some games changing the crossfire method in radeon pro removed the stuttering all together. I also found the 1gb vram was not enough to run games at the settings i wanted to. So i wouldn't say crossfire isnt for everyone, but i would say it isnt for most people that want trouble free gaming. Its best left for those that already have the fastest single card an want extra performance for more monitors or something. In the end i gave up and replaced them with a single gtx660, went with nvidia due to some articles on techreport about them having lower frame latency and smoother gameplay than the AMD equivelant, weather its true or not i didnt take the risk. Now i enjoy smooth trouble free gaming.