I'm using the following minimal interrupt routine for timing: Interrupt: ex af,af' exx ld hl,FrameCount inc (hl) ld a,8 out (3),a ld a,15 out (3),a exx ex af,af' ei reti It works fine on the 83 but causes the 83+ to hang. What can be the problem? PG -- http://www.fastmail.fm - Choose from over 50 domains or use your own