1. A multiprocessing system, comprising: a multithreading microprocessor, comprising: a plurality of thread contexts (TCs) configured as an array, each having a program counter, a general purpose register set for executing a thread, and a register for storing an index of said respective TC within said array; and a multiprocessor operating system (OS), configured to maintain a table of entries, each said entry for storing a CPU-unique value for a respective one of said TCs, wherein said OS comprises a respective thread configured to execute on each of said respective TCs and to read said index from said register of said respective one of said TCs and to read said respective CPU-unique value for said respective one of said TCs using said index.