A pipelined processor for carrying out pipeline processing of instructions, which undergo a plurality of stages, is provided. The pipelined processor includes: a memory-activation indicator and a memory controller. The memory-activation indicator stores content information that indicates whether to activate a first volatile memory and/or a second volatile memory while performing a current instruction. The memory controller is arranged for controlling activation of the first volatile memory and/or the second volatile memory in a specific stage of the plurality of stages of the current instruction according to the content information stored in the memory-activation indicator.