Dual-mode VLIW architecture providing a software-controlled varying mix of instruction-level and task-level parallelism

摘要

This invention is a very long instruction word data processor including plural data registers, plural functional units and plural program counters and is selectively operable in either a first or second mode. In the first mode, the data processor executes a single instruction stream. In the second mode, the data processor executes two independent program instruction streams simultaneously. In the second mode the data processor may respond to two instruction streams accessing only corresponding halves of the data registers and function units. Alternatively, the data processor may respond to a first instruction stream including instructions referencing the whole data processor employing A side function units by alternatively dispatching (1) instructions referencing the A side data registers and the A side function units and (2) instructions referencing the B side data registers and the B side function units. In the first mode, the data processor fetches N bits of instructions each cycle. In the second mode the data processor may fetch N bits of instructions for alternate program counters on alternate cycles or fetches N/2 bits of each of the first and second program counters. The data processor includes interrupt steering and masking control logic allowing instructions to control whether the first instruction stream or the second instruction stream receives interrupts.