I have often wondered why there is a BIOS option on modern motherboards for “spread spectrum.” For a server, you probably won’t need this option unless you have EMI regulations to be concerned with.
this method does not reduce total radiated energy, and therefore systems are not necessarily less likely to cause interference. Spreading energy over a larger bandwidth effectively reduces electrical and magnetic readings within narrow bandwidths. Typical measuring receivers used by EMC testing laboratories divide the electromagnetic spectrum into frequency bands approximately 120 kHz wide. If the system under test were to radiate all its energy in a narrow bandwidth, it would register a large peak. Distributing this same energy into a larger bandwidth prevents systems from putting enough energy into any one narrowband to exceed the statutory limits.
Basically, if you have radio signals or display signals that are operating near your CPU frequency, you would be interested in using this to avoid peak interference and specific frequencies.