Change Vsync Adjust Setting - MiSTer FPGA How-To
You can change speed at which your MiSTer FPGA draws frames to your screen. Go into the ini_settings script and change the vsync_adjust setting.
0 = Most compatible but a couple frames of lag and less smooth scrolling. This is similar to "triple buffering" in other emulators.
1 = A little less compatible, but it has only 1 frame of lag and smoother scrolling.
2 = The least compatible, but it has sub-frame lag and the smoothest scrolling.
If your screen doesn't display an image, reduce the number from 2 to 1, or from 1 to 0, depending on what works.
If you edit your MiSTer.ini manually you can add exceptions for certain cores. For instance:
[Genesis]
vsync_adjust=0
I had to add this option to the end of my MiSTer.ini because my TV couldn't handle vsync_adjust=2 and there were major stuttering issues and sync problems.