SKY-8201 supports 3 types of riser cards: x8+x8+x8 / x8+x16 / x16+x16. The OCU link is the extension signal to support the x16+x16 SKU.
This article will guide you on how to map OCU on the MB and riser card x16+x16 OCU.
All SKY-8201 owners and Advantchers.
Since the sequence fo the PCIe, please note that the OCU 0 on the MB should be connected to the OCU 1 on the riser card, and the OCU 1 on the MB should be connected to the OCU2 on the riser card. Otherwise, the SKY-8201 cannot detect the PCIe card.