1. A method for managing instruction blocks in an instruction window disposed in a processor core, comprising: explicitly tracking ages of instruction blocks currently mapped in the instruction window in which the explicit tracking is performed independently from instruction block order within the instruction window; mapping a new instruction block into an available slot in the instruction window; committing instructions in the new instruction block atomically; and executing, in order of their explicitly-tracked ages, the currently mapped instruction blocks to commit their respective instructions atomically.