Hi, when we accept the risers as correct, it may give this error if it does not see the second processor. But you stated that you saw the processors. In that case, I would have suspected the incompatible or faulty riser at first. However, it is difficult to know this directly. In this regard, I recommend that you consider Marco's advice. You can also check out the threads here. Solved: R630 optional riser - Dell Community Solved: PowerEdge R630 and missing IO Riser card for 2xCPU - Dell Community R630 riser question - Dell Community  
Hello,   We bought a Dell PowerEdge R630 with a dual E5 Xeon CPU inside. When we boot up the system for the first time we encoutered the error "HWC2005 The system board Riser cable or interconnect is not connected, or is improperly connected." After searching for hours on the internet and Dell Forums we think that this server is configured with a non dual CPU supported riser 1. When we take out riser 1 and let riser 3 inside the system, the server will acually boot up without any error. As soon as we get riser 1 inside the server the error showed up again. My question is which part number for the riser 1 is supported for a dual CPU?   Thanks for any response!
Dell PowerEdge R630 correct riser 1 part numbers