I'm running 6 x 4 card rigs, mostly rx470 with 1 rig on rx580. About half the rigs boot fine with no monitor or dummy plug.  The rest need something plugged in to boot. This is odd because the rigs are identical boards ram and cpu. I have one rx580 card that boots and runs fine for around 10 hours then drops to around 4mh. It has nothing plugged in when this happens.  Trying to see how long it lasts with a monitor at present.  Also swapped from claymore to ethminer just in case claymore is the problem. May have to get some dummies on order.