COM Ports COM1 and COM3 use IRQ4. COM2 and COM4 use IRQ3. The majority of PC's have only 2 COM port connectors. System Assembly Basics Phillips and Flat-Head screw drivers are the most common tools needed for disassembly. Paper should be at hand for diagramming connections.
Egg cartons are helpful in keeping screws organized.
Expansion boards should be removed by gently rocking back and forth at each end. Red and blue stripes on ribbon cables indicate pin 1. System Board Repair Mother boards, system boards, planar board, and main logic boards are all interchangeable terms. Older XT planar boards used DIP settings for floppy configuration. Processors Floating-point numeric operations are dealt with by the math coprocessor.