what do you mean? optimus is automatic.
the intel integrated gpu drives the display panel. nvidia gpu is off by default and does not drive the display.
nvidia gpu only activates when you open supported games or you manually assign it to special program like Adobe suite in nvidia control panel.
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If you buy the system for gaming, I suggest you get the 60 Hz G-Sync one or better 120Hz G-Sync. The 60Hz using Optimus is mediocre to me. Screen tearing even with game like CS:GO.