The Late 2012 Mac Mini is no longer my main machine, but there is this problem where when you run a 1080p HDMI display, and set fps on on 40 or more with Vsync off, the game tries to give you the fps but it keeps trying to lock it to 30 fps, this causes a wavy video type lag, not lag spikes. The screen will look like the motion of the picture keeps slowing down in different speeds. When Vsync is on, this issue is gone. I use a Mid 2014 MacBook Pro 13 inch, and it does not have that issue when Vsync is off when driving a 1080p HDMI display. My specs for both computers. What do you think the reason this happens on the Late 2012 Mac Mini. This issue affects all versions.
 

Late 2012 Mac Mini:

2.5 GHz intel dual core i5

HD Graphics 4000

Mid 2014 MacBook Pro 13 inch:

2.8 GHz intel dual core i5

Intel Iris Graphics 5100