Hi, It may seem you could have a faulty CPU slot, but we might need to conclude it. Try swapping, or use the new CPU on slot 1 to check if the processor is working. Then, install the 2nd slot with your previous processor.  Try checking in the logs at BIOS to see if there is any clues.  If none the above, there is nothing much to troubleshoot, as this server is straight forward, and you have already done updating BIOS.
Hello, I've recently decided to upgrade the existing CPU installed on my old Dell Poweredge SC1430 with a second mathed CPU with the exact same specification. The hardware uprgrade was sucessfull, but one strange thing happend, the server starts correctly but doesn't recognize the second CPU in the BIOS. The BIOS post is still mentionning the existing same quad core processor, not the second as he should. I've reset manually the BIOS to the default configuration, but it didn't change anything concerning the recognition of the second CPU. The BIOS version installed is the latest one : V1.4 Could some of you provide me some ways to investigate to try to solve this ? Thanks a lot for your lights, Tiebo.   Technical details : service tag :  2 x matched pair of Xeon processors X5355 @ 2,66 Ghz  
2nd CPU not recognized on dell Poweredge SC1430