NVIDIA published a video on its nTersect blog that shows off some of the features of the Optimus technology. One of the things we didn't know yet is that Optimus enables you to pull discrete graphics cards out of a running notebook, and put them back in later when you need some more power for a graphics-intensive application. This works because Optimus electrically shuts off components in your notebook:
The benefit of electrically shutting off components in your notebook, including the GPU, is that it extends battery life. Compared to a standard notebook with a discrete GPU Optimus can extend battery life up to 2x*. The benefit of immediately turning it on again is, of course, that you get all the graphics and processing capabilities of the GPU at a moment’s notice. Few people ever get to see this demo because it requires a completely open notebook system – no chassis – just the motherboard, CPU, GPU, Hard drive, and monitor, so it is not exactly portable. This demo is really killer with engineering teams that design notebooks. They practically fall out of their chairs when they see it.
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.