1. A multiprocessing system, comprising: a multithreading microprocessor, comprising: a plurality of thread contexts (TCs), each having a program counter and a general purpose register set for executing a thread; and a multiprocessor operating system (OS), said OS comprising a data structure having an entry for each of said plurality of TCs, each said entry containing information describing capabilities of said corresponding one of said plurality of TCs, wherein each said entry further comprises a TC identifier field for identifying a corresponding one of said plurality of TCs, wherein said OS is further configured to populate said TC identifier field for each of said entries with a unique identifier value.