This is not a warranty question, as the components are too old
I have an i5-2405S and a DH67BL. The CPU's graphics are marginal. I am not referring to performance, but integrity. Fox example, if graphics-intensive work is performed, sometimes I will see a message complaining about the graphics driver. I see the same message if I attempt to even slightly overclock the graphics to 26. It's always been this way, making me suspect that chips with lesser power were actually rejects from the i7 or i5-xxxxK lines. So I want to offload the graphics die's work onto a discrete GPU.
My question regards the BIOS option. In BIOS -> Configuration -> Video there is an option called Integrated Graphics Device. The default is Enable If Primary, but another option is Always Disable. Does it make any difference if a discrete video card is installed? I want to make sure the on-chip graphics does as little as possible.
Ivan is absolutely correct. "Enable If Primary" means exactly what is says; the on-chip graphics will be enabled if (and only if) there is no other graphics solution present.
JFFulcrum: you have a Kinsley board, so you can verify this for yourself. The Kinsley board has additional voltage sensors to assist overclockers with performance tweaking. One of these additional sensors monitors graphics engine power. If you have an add-in graphics card installed - and you are running Intel Desktop Utilities - you will see that the graphics engine voltage is set to 0V.
There is other option in BIOS, Primary Video Adapter, defines what graphics will be primary. It is possible to set PEG as secondary, so IGP will be still enabled. In default Auto mode primary adapter selection depends of PCI buses initialization timeline at POST, a sort of probability present in that process. Starting with 6-series chipsets, IGP can be used with PEG together, if not explicitly prohibited by vendor.
I`m on DX79SR, no IGPs at all on that platforms.
Thanks to ivanu_intel and N.Scott.Pearson. That was the best answer one could hope for. I can install a graphics card and be hit by a truck tomorrow, with the next guy not having to worry about modifying BIOS settings.