sc_plastintr     2004 dev/audio.c    			lastdelta = t - sc->sc_plastintr - sc->sc_pblktime;
sc_plastintr     2017 dev/audio.c    		sc->sc_plastintr = t;
sc_plastintr      142 dev/audiovar.h 	u_long	sc_plastintr;	/* last time we saw a play interrupt */