Asus z370-g motherboard, it has pcie16, pcie4 and two pcie1 I connect 3 video cards: in the 16th, 4th through the riser and 1st through the riser - and when turned on, 1 long beep and 3 short, black screen. According to the documentation - "video card error". All 3 cards are working, risers are working, and 2 video cards can work simultaneously without error in any combination of connectors. But 3 cards at the same time is a mistake. What could be the reason?
Page 1-8 of the manual (also page ix and the specifications pages on the website), I don't think it matters, if they are in SLI or not. It supports three displays in daisy chain and total of two graphics cards in x8 and x8 or that is how I read it, what have ASUS support said ?