Hello, I recently added a second graphics card (290X), and I've had Windows 10 for months so I cannot report on whether it's exclusive to that OS.
Anyway, when playing a game that is far exceeded by the hardware, I use Vsync to prevent screen tearing. However, I've noticed since I started using CrossFire it seems as though Vsync does nothing. My fps is constantly in the 90 range on a 60Hz monitor. I just started Fallout New Vegas and it seems my fps caps at 120. I know Vsync has an adaptive cap thing, but it should never go above the refresh rate. When I use third party software to lock my fps to 60, I get even worse tearing. Some other games, my fps seems to cap at 30 with Vsync, even though when I turn it off I get 250fps (Murdered Soul Suspect). When I disable CrossFire everything works normally, cap is 60 for all games. I know at least in New Vegas that's not a product of adaptive capping because with it off it still goes into the 100 range. I've tried with the 15.5 beta drivers and the ones provided in Windows Update. I'm on the most recent build (10130) of W10.
I know I signed up for these glitches by trying beta software, I'm just reporting this in case it's not known (and maybe it's not caused by W10 either?)
Thanks for any help!