I wish to use three monitors, but my PCIe graphics card only has two DVI outputs. My motherboard, an ECS A880GM-M6 Black Series, has onboard graphics, but it seems to be disabled when the PCIe card is installed (all the related BIOS options vanish). I am running GNU/Linux, but the onboard graphics hardware is not detected; it does not show up in the output of
lspci, and it seems to be disabled at the hardware level.
Several questions like How can I enable onboard graphics AND dedicated card simultaneously? seem to indicate that this is usual behavior, but the motherboard documentation states that some ATI graphics cards (4xxx series?) can be used in Crossfire mode with the onboard graphics hardware (briefly mentioned here, although it's spelled "GrossFire", along with more details in the motherboard manual). Since this is possible, it seems like there should not be any hardware conflict. My graphics chipset is from NVIDIA, but I don't want to use Crossfire, I only want the extra outputs.
Therefore, it seems that there should be a way for me to use the onboard graphics card to support a third monitor. However, I have been unsuccessful in finding any documentation for this situation. Is this possible? If so, how can I accomplish it? If not, why not?