I could be wrong with my ever-fading memory however IIRC it wasn't until the PII that we had different sockets for different manufacturers, so the 386 would be able to have an Intel or AMD taking the same pins so I don't think it's a manufacturer choice feature.. not that I know what it IS for.
Do you know the make and model of the motherboard? Maybe we could find the manual somewhere just for kicks and figure out why it's really there.
Do you know the make and model of the motherboard? Maybe we could find the manual somewhere just for kicks and figure out why it's really there.