I have another problem with OpenGL: DOSBox plays perfectly in OpenGL windowed mode, but not in full screen mode. When I switch to full screen, the sound becomes very choppy. It's not a processor power matter because in windowed mode the same application consumes about 60% CPU.

Another strange thing is that all animations play smoother in OpenGL full screen than any other mode, perfectly syncrhonized with the monitor's vertical refresh. The refresh in OpenGL fullscreen modes seem to be at 60 Hz rather than the 75 Hz of standard VGA modes. So, it seems DOSBox is adjusting its speed to the monitor's refresh rather than adjusting the monitor refresh to the required emulated VGA mode speed.

And I have another problem with OVERLAY mode: if I start DOSBox in fullscreen mode directly, it works fine. But if I start in windowed mode and then change to full screen mode, DOSBox quits.