In the BIOS setup utility of ASUS M3N78-EM, there is an option to set iGPU Frame Buffer Size instead of Hybrid SLI (as has been stated in the manual). What might be the reason for this, and what does iGPU Frame Buffer Size relate to?
The iGPU stands for Integrated Graphics Processing Unit. That setting controls the amount of memory you give to the integrated graphics on your motherboard. Typically this can be values from 32MB to 512MB depending on the board.
I believe when Hybrid SLI is enabled which combines your iGPU with an external discrete GPU, the option to control the amount of memory is turned off since this is managed by the board.
iGPU stands for integrated Graphics Processing Unit. iGPUs share system memory (RAM) with the other parts of your system. The Frame Buffer size setting allows you to state how much memory is available to the integrated GPU (this goes into much more depth, but that is the Reader’s Digest abridged version).
Now, this allows for change because the iGPU settings started gaining prominence with the advent of nVidia’s Hybrid SLI technology, which will allow you to use an iGPU and a Discrete GPU (dGPU or video card) in an SLI format to boost performance or save power. They need to allow you to turn it on or off because this tech is only available (currently) on Windows Vista (and I would assume Windows 7), so people running another OS would probably want to change this setting.