@Gelip
Before I get nuts, I go back to my Asrock z370 Fatalty gaming K6 board.
Oh..what a nice board. At once normal Windbg works through its internal COM1 port.
Tomorrow I try your methode on this board with one after the other of all my PCIe serial slot cards. By the way, I just ordered your Card PCIe Sunix SER5427A also
Dietmar