My L502x + PE4C + GTX970 setup has some annoying boot up problem, so I spent some time doing experiments and some research, here's what I found regarding these two special signal lines.   Basically they are related to how a motherboard initialize a device. Per https://pcisig.com/sites/default/files/specification_documents/MiniEx_M2_ECR_PERST_CLKREQ_Power-up-Reqts_20140918_Final.pdf, we can learned that for a normal motherboard + pcie devic