A+ Exam Objective 3.7

3.7 Summarize power supply types and features.

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Welcome to Exam Notes by CertBlaster! In this article, we will cover Core 1 objective 3.7 Summarize power supply types and features.

Input 115V vs. 220V

When hooking up the power to your system, one of the main things you’ll notice is that directly near the three-prong power connector is a small switch that reads 115/230. This switch allows the PSU to accommodate international voltage and allows you to provide the correct voltage to your PC.

24-pin motherboard adapter

The main function of a power supply is to provide the correct amount of power to the motherboard. The connection between the power supply and the motherboard has evolved from a single connector into a two-part connector, the 20+4 pin connector. This connector will supply the appropriate power to where it is needed. In the image below, the white connector is the legacy connector and can be compared to the newer 20+4 pin. On the newer 20+4 pin, the additional four pins are free and can be moved over in order to provide an additional 12 volts to the processor. Both connectors shown below are the main connectors to the motherboard and operate at +3.3V, +/- 5V, and +/- 12V.

Motherboard power connectors: 20 (white) and 24 pin (black).

Output 3.5V, 5V and 12V

Here’s a look at the connectors you will find on an ATX power supply. Listed first are the connectors that supply power to the drives and provide supplemental power to the motherboard.

• Wattage rating

Any discussion of a power supply will include wattage. For a power supply, wattage is the amount of power that can be delivered to the system. When selecting a power supply, ensure you are delivering the correct amount, i.e. an amount that will support the sum of the components your system will have. Different processor and memory combinations will have different power requirements. Use an online wattage calculator to determine your needs, then add on another 10% on top for power peaks.

Number of devices/types of devices to be powered

This is a crucial element of power supply selection. When replacing a power supply, always select a replacement power supply with the same wattage or higher. For a new build, you can calculate your power needs using an online wattage calculator. You’ll be surprised how much power you need. As you add drives, expansion cards, and fans you’ll see your power requirement rise. The motherboard, processor, and memory will also play a role. For example after using one power supply calculator, the calculated requirement for an older processor was 502 W (this is a load of 452 W + 10%). When we plugged in (😊) values for the latest Socket/ CPU, our load jumped to 681 W + 10% = 731 recommended wattage. Always get a bigger power supply than you need.  You’ll never know when you may want to add a hard drive or DVD player.

That’s all for objective 3.7. Good luck on the test!

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