BITS 16

mov cl, 0xFA

.repeat:

in al, 0x60
cmp al, cl
je .repeat
mov cl, al

mov ax, 0xB800
mov es, ax

mov al, cl
mov ah, 0xE4
mov bx, 0x0000
mov [es:bx], ax

jmp .repeat

times 510-($-$$) db 0
dw 0xAA55