> My system apparently favors D3D (Intel Core i5-4570, GTX 970, Win10 x64):
> mame64 pacman -nothrottle -str 30 -video d3d
> Average speed: 4430.15% (29 seconds)
> mame64 pacman -nothrottle -str 30 -video opengl
> Average speed: 197.96% (29 seconds)
> mame64 pacman -nothrottle -str 30 -video bgfx
> Average speed: 573.56% (29 seconds)
> Ran twice with similar results. I remember nvidia GPUs once favored OpenGL, but I
> guess that was awhile ago.
I'm going to guess that in your graphics driver you have driver some internal setting set to forcibly sync video to signal and is not allowing you to unthrottle, even if MAME allows it. Check your settings via your card's desktop manager software and/or make sure vsync is off in MAME before retesting.