NVIDIA Optimus: The Video Card Is Optional
Why? Because with Optimus when the GPU is not needed it is completely powered off automatically and seamlessly WHILE the rest of the system is up and running – the power to the PCI Express bus, the frame buffer memory, the GPU - everything. This is in contrast to switching the GPU to a low-power state or to ‘idle’, which would still draw power. You can of course prove the GPU is electrically off by using battery benchmarks and software tests. But the fun way to prove it is to physically PULL THE GPU out of the system while the system is still on and working.
In the video, the company does just that. I was excited when AHCI technology brought us hot-swappable SATA; hot-swappable video cards are another matter altogether. End-users are highly unlikely to go pulling their video cards out regardless if the notebook is on or off, but as tech demos go, this one is a doozy.