The time unit, specified by the unit argument, can be one of cycles, s, ms, us, ns, ps, m or h.
The command sets the processor switch time globally if the cell argument is omitted, and all existing cells will have their time quantum reset to the new value, and cells created later will use the new value.
Without arguments, set-time-quantum prints the time quantum of all cells in the system, as well as the default time quantum (if set). In this case the output is printed also when run non-interactively.
If the argument is given in cycles the time_quantum attribute is unset. And if the argument is given in seconds then the cpu_switch_time attribute is unset, both in the sim class.
When used in an expression, the command returns the given value, in seconds or cycles, or an exception is raised. Without arguments the current time quantum is returned, or -1 if no cell exists, or if there are cells with different time quantum values.