AH = 83h AL = 0 set interval = 1 cancel interval (PS/2) CX,DX = number of microseconds to wait (976 ęs resolution) ES:BX = pointer to memory flag (bit 7 is set when interval expires) (granularity is 976 microseconds) on return: CF = 1 if function already busy AH = 80h for PC = 86h for XT & AT - available on the AT (BIOS after 1/10/84) and PS/2's except 30 - designed for use in simple multitasking