PCIe hard IP and PeG (PCIe graphical slot)

Hi,

Does anyone know why the PeG slot on the motherboard cannot detect the FPGA with PCIe hard IP? I see this problem on all my PeG slots and it is also confirmed by one of Intel's partner but there is no explanation why PeG slot cannot detect FPGA with PCIe hard IP.

One option is to disable the PEG port (change it to non PEG port) in the BIOS to make it work. However, some motherboards don't allow this option (cannot change to non-PEG port).

Is there anything else I can do to make the FPGA with PCIe IP works in PEG port?

Thanks