State Vectors:
Priority levels 5 and 7 are reserved for the Nucleus. Priority 0 is reserved for the idle process. If you add a (faultable) process at that level, you must also add a state vector for it. Note that a state vector is needed for every process that is running, pre-empted, or faulting (page, frame, ...). Processes waiting for conditions or monitor locks do not need state vectors. RRA pushed up these numbers on May 2, 1986 to be conservative.
STATEVECTORSIZE: 20;
STATEVECTORCOUNT: 0, 2; -- IdleProcess.
STATEVECTORCOUNT: 1, 20; -- Background.
STATEVECTORCOUNT: 2, 32; -- Normal.
STATEVECTORCOUNT: 3, 20; -- Foreground.
STATEVECTORCOUNT: 4, 12; -- Client3.
STATEVECTORCOUNT: 5, 4; -- FaultHandlers
STATEVECTORCOUNT: 6, 4; -- RealTime
STATEVECTORCOUNT: 7, 4; -- SwatWatcher