After adding a CPU to a server, which factor should be verified if the server fails to pass POST?

When troubleshooting a server that fails to pass the Power-On Self-Test (POST) after a CPU has been added, verifying the stepping of the CPU is crucial. CPU stepping refers to a specific version of a CPU that may include certain bug fixes or improvements over previous iterations of that chip. If a CPU with an incompatible or unsupported stepping level is installed in the server, it may lead to hardware conflicts and prevent the server from successfully passing POST.

Step and compatibility can be significant in ensuring that the CPU operates correctly with the motherboard and other components. Server motherboards often have a list of supported CPU steppings, so confirming that the new CPU's stepping is listed as compatible is an essential step in the troubleshooting process.

In contrast, while ECC (Error-Correcting Code) memory, CAS (Column Address Strobe), and bus size are important factors in overall system functionality and performance, they are not directly related to the failure to pass POST specifically associated with the installation of the CPU. Issues with those components might manifest differently, such as memory errors or performance problems, but they wouldn’t typically cause a direct failure in the POST sequence triggered by CPU installation. Thus, checking the CPU stepping is the most relevant approach in this scenario.