1. A system comprising: a processor having a vector processing mode and a multithreading mode, the processor configured to operate on one thread per cycle in the multithreading mode, and the processor comprising: a program counter register comprising a plurality of program counters, the program counter register being vectorized, and each program counter in the program counter register representing a distinct corresponding thread of a plurality of threads; the processor configured to execute the plurality of threads by activating the plurality of program counters in a round robin cycle.