What [usertime] and [systemtime] tell you together should add up to the amount that [cputime] tells you. reset timer trigger output value in milliseconds While [cputime] gives you the total time spent in the pd process, therefore excluding any time spent running any other programmes, time spent running pd.tk, and time spent doing nothing at all, [systemtime] also excludes whatever is NOT run in the kernel. In C language, this is the "stime" feature of the times() command.