Presentation I did when I once worked for one of Barbados Top Tech Companies:
What Is A Computer Power Supply ?
What is a Computer Power Supply?
A power supply is the component that supplies power to a computer. Also, known as PSU (Power Supply Unit), most computers can be plugged into a standard electrical outlet.
The Power Supply Unit then pulls the correct amount of electricity and converts the alternating current (AC) to direct current (DC).
Power Supply Units also regulates the voltage to eliminate spikes and surges common in most electrical systems. However, not all Power Supplies do an efficient power regulation job, so a computer Power Supply can still be vulnerable to voltage fluctuations.
PC Power supplies are usually measured in watts, so the more power the computer needs, a higher wattage power supply will best for that PC. Also, modern power supplies are rated based on their efficiency.
Computer Power Supply Cable Guide
Inside of A Modern Computer Power Supply
Modular vs Non-Modular Power Supplies
Non-Modular Power Supply
This is when the all the cables are attached to the power supply and they all are good to go. Typically, in a system build, not all cables are used.
The downside of having a non-modular power supply is that cable management can be messy depending of the type of computer case the power supply is install in.
Bad cable management can mean the difference of good and bar airflow, which can be a result of the operating temperature in your computer case.
Modular Power Supply (Semi /Full)
A typical semi-modular power supply usually has only the essential cables attached to it, such as; the 24pin ATX cable and the 8pin CPU cable. There is less more clutter than a non-modular power supply and less expensive than a full-modular power supply.
Full-modular power supplies come with no cables pre-attached whatsoever! You only attached the cables you need. They might be the most expensive power supplies, but you will get the best freedom of routing of your cables, for the best cable management and your air flow will be optimized to the maximum.