A:Answer What kind of cable? Also with some motherboards, you'll need to get into the BIOs to switch from onboard output to PCI output, if you have a dedicated graphics card. So if you had HDMI, and a dedicated graphics card, you'd need to connect monitor to top-most HDMI port, get into BIOs (usually tapping DEL or F2 keys while it's booting usually will get you there, but not always) and change from onboard to PCI video output, reboot then you can move the HDMI to bottom most port.