mov ax, 4F15h ; DDC - INSTALLATION CHECK
xor bl, bl ; = 0 for to get the monitor information
int 10h
cmp ax, 4Fh
jnz NODDC
mov ax, 4F15h ; DDC - READ EDID
mov bl, 1
xor cx, cx
xor dx, dx
mov di, OFFSET EDID
int 10h
mov eax, 0FD000000h ; Text-identifier V/H range
mov bx, 36h
cmp [di+bx], eax ; di+36h detailed timing #1
jz short H1
lea bx, [bx+12h] ; (add bx,12h)
cmp [di+bx], eax ; di+48h detailed timing #2
jz short H1
lea bx, [bx+12h]
cmp [di+bx], eax ; di+5Ah detailed timing #3
jz short H1
lea bx, [bx+12h]
cmp [di+bx], eax ; di+6Ch detailed timing #4
jnz NODDC
H1: cmp BYTE PTR[di+bx+6], MAXHZ
jb NOHZ
cmp BYTE PTR[di+bx+8], MAXKHZ
jb NOKHZ