The reason why is a dx fullscreen app has a much higher task priority than a windowed app. A windowed app has less priority than any system task. The fullscreen App has an extremly high prirotiy, so high that it may crash the system when you don't let windows "breath" from time to time with a Delay, waitkey, flip true or something like that that allows the OS to utilize Blitzes Idle Time.
A very long time somebody posted a solution that would allow to set the Processes Priority. It should be possible using the Windows Api with a decls call. Although even then you may not get the same priority as a fullscreen App.
A very long time somebody posted a solution that would allow to set the Processes Priority. It should be possible using the Windows Api with a decls call. Although even then you may not get the same priority as a fullscreen App.