How to Tell If It's the Motherboard or the CPU That's Dead

By Scott Shpak

When your computer is completely unresponsive, it's natural to feel a sense of panic, since it may seem that you've lost your work, photos and music. There are, however, many non-fatal conditions that can turn your computer into a temporary paper weight. The power supply, for example, can bring everything to a screeching halt. When you have a motherboard or CPU issue, it's harder to identify without tools for testing or spare parts to exchange -- things that aren't on hand for the average computer user. There are, however, indicators that usually point to the culprit.


Because the power supply is used by all systems in a computer, it's the most common source of computer failures. Watch for loose connections as well as failure of the power supply itself.

Distinguishing Between The Pieces

Upon opening a computer case, it may appear that the CPU and motherboard are one piece but in fact, the motherboard is the printed circuit board that occupies the largest space in the average computer tower. It has a socket of specific dimensions, into which a compatible CPU is inserted. Contemporary computers can have rather impressive assemblies attached to the motherboard, usually around the center of the board. This is the heat sink and cooling fan arrangement to keep the CPU within its operating temperature range. There's usually a tiny speaker on the motherboard, often round, black and the size and shape of a stack of several five-cent coins, though other shapes and sizes occur.

CPU Cooling Issues

A quick visual inspection of the cooling fan may give a clue that the CPU has problems. This requires removal of side panels in computer towers or access panels for laptop computers. Heavy dust build-up lowers the efficiency of the fan and is a sign that all is not well. But you can't just simply check for spinning fans, since multi-speed fans operate based on the temperature of the CPU. If your computer has been turned off, the CPU will be cool already. If your computer does operate for a short period of time after turning on, it is likely that CPU overheating is the cause of the computer failure.


Unplug power supplies from wall outlets and remove the battery from a laptop before attempting to work inside any computer.

Computer Speaker

When your computer is started, a short beep is common. Before the computer loads an operating system, the motherboard's native software, called the BIOS, does a power-on self-test. Beeps are used to communicate problems, and different manufacturers use different beep codes. An unresponsive computer that is now also silent at startup strongly indicates a motherboard issue.

Advanced Troubleshooting

As mentioned, these diagnostic steps aren't conclusive. Advanced users may follow a troubleshooting flowchart and systematically identify where a problem originates, but this could require replacement of a CPU or trying the CPU in another motherboard.