The LPT & IDE tester is for testing open circuit or short circuit occurs on the motherboard, hard drive IDE port and parallel port.
Motherboard error always shows as below: no display, fail to turn on, fail to find the hard drive or unstable motherboard.
All these problems can be tested by LPT & IDE tester.
As long as open circuit or short circuit can be tested, the error would be south bridge.
The motherboard serial port error can be tested by serial port testing card. Just connect the IO chipset to the data cable and control signal. (If the motherboard does not display, the serial port card can also be used to test. The motherboard would not work when the IO chipset is damaged by external error.)