When Riser 2 is installed on R640  having second CPU is mandatory.
After removing CPU2 and it's memory modules I got this message: UEFI0147 The system hardware or cabling configuration is invalid. Do the following: 1) Make sure the system cables, risers, and CPU configuration are installed correctly. 2) Reseat each PCIe riser and reconnect the cables. For more information, see the system Owner's Manual. I cleared NVRAM, but the message is still there. What I managed to get is to boot into system by disabling wait for F1/F2 on error. Is there a way to get rid of this message other than putting back CPU2? PowerEdge R640
R640 - UEFI0147