thanks for the replies guys. I've also been reading on dummy plugs. is it an issue with 775 mobos to have dummy plugs on gpus which aren't connected to a monitor?
no problem on linux with nvidia
on windows you need one gpu connected to monitor
If you are using the PCIE 1-16x slot for GPU; disable the onboard. Trust me. Nothing but heartache.
The socket 775 Mobo's are fine. I have even used the first gen AMD X64 motherboard/CPU from an old dismantled name brand home pc.
As for the issue with a monitor needing connected; that's dependent on the driver or GPU itself.
I have never heard of the OS itself causing this to be an issue.
I have personally never once had a nvidia > 6 series card ever need a monitor or dummy plug plugged in for the miner to boot and operate correctly. I only have an issue if its my home gaming PC with multiple GPU's, and I left a monitor unplugged when I booted; it didn't want to pick up my monitor as primary unless it was on the GPU populating the PCIE 16x slot #1 for some reason... but my monitor is always plugged in, so no issue there.
I have only heard of this issue with AMD, and specifically RX series, though it may encompass more than just those.