A pipelined instruction decoder for a multithread processor including an instruction decode pipeline, a valid bit pipeline, and a thread identification pipeline in parallel together, with each having the same predetermined number of pipe stages. The instruction decode pipeline to decode instructions associated with a plurality of instruction threads. The valid bit pipeline to associate a valid indicator at each pipe stage with each instruction being decoded in the instruction decode pipeline. The thread identification pipeline to associate a thread-identification at each pipestage with each instruction being decoded in the instruction decode pipeline. The pipelined instruction decoder may further include a pipeline controller to control the clocking of each pipe stage of the instruction decode pipeline, the valid bit pipeline, and the thread identification pipeline. The pipeline controller may invalidate an entire thread of instructions, squeeze out invalid instructions, and/or conserve power by selectively stopping the clocking of pipestages.