Problems with BIOS delay function (INT 15h / AH = 86h)

Question

I began studying assembly this year in my school, and we just started learning about pixels.

Our teacher gave us some code and told us to mess around with it, he also to

Answer 1

There is a weird fact, about int 15h ah=86h you also need to set al=0, unless it get an erratic behavior

Delay Code:

mov al, 0 mov ah, 86h mov cx, 1 mov dx, 2 int 15h

I discovered it with try-and-error method and I realize when al=0 it works.