The nVidia Optimus simple idea
Optimus is to use an IGP (Integrated Graphic within chipset, such as MCP79 GeForce 9400M or GMA 950) for mainstream 2D use, and use of a discreet GPU (9600M GT, HD 4670, HD 4850 …) to display multimedia HD content, 3D content, dynamically.
The simplicity of Optimus is that the IGP is connected to the display (1 or 2 monitors), and the GPU just output into videomemory buffer, without any connection to any display.
How does this works?
The buffer output of 3D game or HD multimedia content is streamed over PCI-express to the main memory where the IGP get it to be displayed. No physical modification if you have a mini-PIC-express port, you could even think using basic GPU on ExpressCard/34 to complement an Intel GMA!
Moreover you could create a laptop motherboard without any GPU, displays output connected to the IGP, or add GPU with PCI-express port as an option. And the most of the time you could just shutdown the GPU and let IGP handle OS 2D interface (or even aero for Vista or Windows 7).
