What’s a little undocumented behavior between friends?

(NOTE: this post will get very technical. Some knowledge of 16-bit x86 assembly will help). From the MPC60 code that computes the duration of a note in timer ticks: seg000:5659 sub dx, dx seg000:565B mov cx, 0Ah seg000:565E div cx seg000:5660 jnz short loc_5665 seg000:5662 mov ax, 1 seg000:5665 seg000:5665 loc_5665: seg000:5665 mov bx, ax […]