bad cpu symptoms

when CPU is abused by its owner it starts showing performance degradation. But how to tell if your CPU is damaged and working properly or not. There are some bad CPU symptoms that a processor shows before dying.
Bad CPU Symptoms

Lockups and overheating immediately before PC shuts down. CPU overheating
Charred motherboard or CPU
Undue stress or overclocking
A power surge or unstable voltage
Bad motherboard