Originally Posted by MEC-777
I discovered getting crossfire to work properly on 290's can be a bit tricky. There are a lot of little things/tweaks that sometimes need to be done to get it working "just right".
When I first installed my 2nd 290 it took me a few days to figure everything out and start seeing the proper performance gains it should be providing. Until I got it working right, I did see the same or worse performance in a number of games. The biggest issues for me was getting both cards clocking the same and preventing power tune from causing one of my cards to down-clock even though it was nowhere near thermal limit. Now that I have it all figured out and setup correctly, both my cards clock down to 300/150 at idle with the primary card clocking up a little from time to time depending on desktop load. In games, both clock up together to 947/1250 (stock) and they both stay glued there the whole time, regardless of load.
Here's what I would suggest for @Shweller
to try: (This is the process I follow to update drivers and ensure my crossfire setup works properly thereafter)
-Download latest version of DDU.
-Download latest AMD drivers (15.10 beta) from AMD's support website.
-Exit MSI AB (close it down)
-Uninstall your current AMD drivers via add/remove programs in control panel.
-Shut PC down (don't restart). With PC shut down, unplug the PCIe power cables from the secondary card but leave the card installed. The PC just simply won't detect it.
-Power up PC and run DDU - it will ask you to restart in safemode, do it and follow the steps to completely remove all AMD software. Then restart PC.
-When PC boots back into windows, run and install the new AMD drivers (15.10). Restart as prompted.
-After restart with the new drivers installed, check and make sure it installed correctly (open CCC (catalyst control center) and check version number etc.) If everything looks good, shut the PC down again.
-Kill the power switch on the PSU just to be safe, wait ~10-15 seconds, then reconnect the PCIe power cables to the secondary card. Turn the PSU back on and power up the machine.
-When you get back into windows give it a minute to detect the 2nd card. If it doesn't open a prompt to enable crossfireX, open up CCC and enable Crossfire. (make sure you also check the box that says "enable crossfire even for applications that have no crossfire profile).
-While you're in CCC, go to the performance section and disable overdrive.
-Next, open up MSI AB and go into settings. Check the box to sync the cards so they both run at the same clocks. You can check the box to disable ULPS, but I left mine enabled and it's been fine (it's an optional thing). Apply and close the settings.
-In AB, set the power limit to +50% (as high as it will go). No harm will come from doing this. It will just make sure power tune doesn't downclock when it shouldn't. Set the GPU core clock to 947 (or what ever is stock for your cards) and the same for the memory - 1250 or what ever it should be. Click apply and then set that as profile #1 and click the little dot that says "apply OC on startup".
-Now, go run a 3D application (I like using unigine valley as a quick easy test) and watch your GPU clocks (if you have a 2nd display watch AB on the 2nd screen, if not, just alt-tab out while the program is running and look back to see what they were doing. Just keep in mind; some applications will drop out of crossfire mode (drop down to one card) when you alt-tab out and back in (valley does this)). They should sit at 300/150 at idle and ramp up to max stock clocks under load. If both cards ramp up together and stay that way, you should be good to go. GPU load should also be matched on both cards.
Let me know if that does the trick or if you have any trouble with any of those steps. Crossfire can be finicky and the silliest little thing(s) can cause undesirable performance if it's not working just right.
Clear as mud?