Do NOT waste your time and reinstall your Windows or whatever, these are the types of issues you sign up for when you choose things like multi GPU cards, or jumping on brand new operating systems.... that's the game you signed up for basically...
I mean unless you don't know much about computers and just had your local shop built you the most expensive one and you were expecting to play everything flawlessly maxed out at 4k... unfortunately it should be, but it's not how it works in the PC world....
me personally I got 2 crossfire R9 290x cards, and in Windows 8, sure I was able to play it maxed out at 1440p at 60 fps v-synced..... BUTTT I would get the dreaded AMD stutter, and microstutter often, where frames would just drop down to 50 and as low as 40 for a second or two then go back up and lock itself to 60, especially when walking through big cities..
With Windows 10, I am experiencing NONE OF THIS........ fully locked v-synced 60fps almost 100% of the time..... I have to say I am enjoying Win 10 like I enjoyed Win 7
