Method and apparatus for implementing two-tiered thread state multithreading support with high clock rate

A method and apparatus are provided for implementing two-tiered thread state multithreading support with a high clock rate. A first tier thread state storage stores a limited number of runnable thread register states. The limited number is less than a threshold value. Next thread selection logic coupled between the first tier thread state storage and a currently executing processor state, picks a next thread to run on a processor from the limited number of runnable thread register states. A second tier thread storage facility stores a second number of thread states that is greater than the limited number of runnable thread register states. A runnable thread selection logic coupled between the first tier thread state storage and the second tier thread storage facility, selectively exchanges thread states between the first tier limited number of runnable thread register states and the second tier thread storage facility.