Hab sowas gefunden. Weiß allerdings nicht, was da genau passiert.
mov ax,$5301
xor bx,bx
int $15
mov ax,$530e
xor bx,bx
mov cx,01
int $15
mov ax,$530f
mov bx,1
mov cx,bx
int $15
mov ax,$5308
mov bx,1
mov cx,bx
int $15
mov ax,$5307
mov bx,1
mov cx,3
int $15