Opengl is slower than d3d in a game.

1. specially in lower os d3d is faster than opengl in playing a game.
when using opengl, the speed has slow, but in the d3d the low os fast .
want to know the causes. difference between opengl and d3d?

Could you explain me??


2. I'm using the ati x800 graphic card.
the drive support the opengl, but in the d3d my graphic card breaks on screen.
by using alt+tab or restarting, I can use d3d on the game.
but don't work well than opengl.


why does the crushed screen happen on d3d??

let me know the causes..thanks....