I have my main gpu run my 3 main screens, and my fourth is just for other stuff, but can i put a high end game on that screen? because that screen plugs into the motherboard will it be slower?
Whatever program is running on the monitor attached to the motherboard will use the motherboard/CPU graphics.
The dGPU will drive the three monitors. Performance for that will depend on whether all three run at the same time as a virtual monitor or if you run one only for a game.
What happens if i have a windowed game and i split it between two monitors? one with the onboard gpu and one with the pcie gpu? will half the game run at a slower fps?
What happens if i have a windowed game and i split it between two monitors? one with the onboard gpu and one with the pcie gpu? will half the game run at a slower fps?
No.
AFAIK you can't run a game on multiple monitors unless they're all connected to the same graphics card.
There may be some rare exceptions, and I do know DX12 in theory allows the iGPU to assist. Even then, one graphics card would be in charge of the output, and the frame rate would be identical between monitors.
Multiple monitors are seen as a virtual screen (i.e. 5760x1080 for three 1920x1080 monitors). Everything is processed like normally and at the end of each frame it's sliced up into three pieces and sent off to the appropriate monitor.
It looks like my fps drops, depending on which screen i have 50% or more on... If i have half of the game on the left screen i get 120 fps, and on the right i get about 70-80.
Does that mean iv switched gpu for the game? or im just not sure lol.