The Advanced Microcontroller Bus Architecture (AMBA) specification defines an onchip
communications standard for designing high-performance embedded microcontrollers.AMBA is one kind of on-chip buses, used to connect many components together to build a soc.OCP is only for a peer to peer level protocol,it is an general interface may be attached to an AMBA bus. instead of interfacing irectly OCP allows u a general interface to any device which is again an OCP compatible.AMBA bus is a bus the difference is an interface and bus.