Let me explain something, every power supply will not pass through to the output any spikes on the input line. A big enough spike on the input line could, however, damage or destroy the power supply (which might, incidentally take out something on the motherboard as it fails).
OCP stands for Over Current Proctection. It is a feature that reduces the output instantly if the LOAD were to have a short circuit, such as a voltage regulator on a motherboard failing can do. It also protects the power supply from that over current load condition.