Server motherboards come in a variety of form factors, each designed for different types of servers and applications. The most common form factors are: EEB (Extended Extended ATX): The largest form factor, designed for high-end servers with multiple CPUs and expansion slots. E-ATX (Extended ATX): A smaller form factor than EEB, but still suitable for servers with multiple CPUs and expansion slots. ATX (Advanced Technology Extended): The most common form factor, suitable for a wide range of servers. microATX: A smaller form factor than ATX, suitable for small servers or servers with limited expansion requirements. mini-ITX: The smallest form factor, suitable for very small servers or embedded systems.