I want to use 100% CPU on system that requires that to run the game smoothly, but not on ALL systems.
You see that is the problem because:
The game uses delta timing, and can run as fast as it likes without messing up the game timing.
You are going to have to decide on an acceptable frame rate...maybe when the game first starts up grab the millsec, then enter a loop to count out say 100 VWaits...see how long that took so you have some idea of what the users refresh rate is and calculate the target FPS... then as the game is running keep an internal FPS counter and every few seconds or so check if it's greater then the calculated target FPS rate...if it's over then start heavily useing the Delay 10, giveing up OS timeslices to other apps...if the FPS is lower fire up the delta time, frameskip routines, all that stuff...
If you want to use 100% CPU on system that *requires* that to run the game smoothly, but not on ALL systems....then you are going to have to qualify what those requirements are.