Mark please clarify : So I don't need to speed up my logic code for slower machines?
Yes you do - it only handles the case when the machine is 'fast enough'.
What about hz refresh rate/flicker? I don't understand this clearly...
It tries to use vsync if possible. If not, it disables vsync and uses an internal timing system. This makes for much smoother graphics than if the vsync is left enabled and 'fighting' the update rate. It also provides surprisingly flicker-free results for systems with no vsync.
See mod/brl.mod/glmax2d.mod/glmax2d.bmx for how it all works.