Apologies if this has been covered recently, but I thought I'd share a success that may or may not be helpful to some. 

 

Specs:  i7-4770, 16GB, Q87, IGD, GT730, 

 

I was playing around with a Win10 VM and everything was working great - until I rebooted the server.  I wasn't trying to pass through the only GPU as the server was given the onboard.  Anyway, a bunch of messing around happened (BIOS dumps/stubs/etc.) and I tracked down the problem:

 

It turns out the motherboard BIOS will 'overwrite' the GPU selection setting (igd vs. pcie) if it doesn't detect a monitor connected to what has been selected.  I was trying to run the server headless so I had the only monitor connected to the "passthroughed" GPU.  This didn't seem to change regardless of the BIOS settings (auto, specified, multi-monitor...  didn't matter)

 

Obviously this is a good idea if you're trying to get a normal computer to post but has the bios setting mis-selected; that way you can still see the boot menu.  Oddly enough, this doesn't change the selection in the BIOS settings, but I feel that unRaid/KVM gets confused and can't passthrough what has now become the de facto default GPU.  

 

So, if I have the monitor connected via HDMI to the onboard during server boot, then swap it over to the card after unRaid has loaded, but before starting the Win10 VM, everything works great literally every time.  If I leave the monitor connected to the passthrough GPU during a server reboot: Code 43 literally every time.  I have repeated/verified this more than 10 times (usually because I forget to swap the cables.)

 

I haven't tried a dummy HDMI or VGA plug as of yet.  That is the next step.  

Thanks dude! IT WORKED :D After hours of googling and fiddling around you have finally solved my issue. Also i signed up here just to write this :)