Are the serial ports, parallel port(s), and mouse port (assuming it's PS/2) all directly onboard, or do they connect to the mobo via cable/ribbon? If the latter, it's most definitely an AT. But if they are all onboard, then it's most likely an ATX.
Are the serial ports, parallel port(s), and mouse port (assuming it's PS/2) all directly onboard, or do they connect to the mobo via cable/ribbon? If the latter, it's most definitely an AT. But if they are all onboard, then it's most likely an ATX.