INT 15 - SYSTEM - PROGRAMMABLE OPTION SELECT (PS50+) AH = C4h AL = subfunction 00h return base POS register address 01h enable selected slot for setup BL = slot number (1 to 8) 02h disable setup for all slots (enable adapter) Return: CF set on error DX = base POS register address (if subfunction 00h) SeeAlso: AH=C6h