Catalog / Computer Hardware - Power Supplies Cheat Sheet
Computer Hardware - Power Supplies Cheat Sheet
A comprehensive cheat sheet covering essential aspects of computer power supplies, including terminology, standards, troubleshooting, and efficiency considerations. This guide helps users understand and select appropriate power supplies for their systems, ensuring stability and performance.
Fundamentals of Power Supplies
Key Terminology
AC (Alternating Current) |
The type of electrical current supplied by wall outlets. Power supplies convert AC to DC. |
DC (Direct Current) |
The type of electrical current required by computer components. Power supplies provide DC voltage. |
Watt (W) |
Unit of power, calculated as Volts x Amps. Indicates the amount of power a component requires or a PSU can deliver. |
Volt (V) |
Unit of electrical potential difference. Common voltages in PCs are 3.3V, 5V, and 12V. |
Ampere (A) |
Unit of electrical current. Indicates the amount of current flowing through a circuit. |
Efficiency |
The ratio of output power to input power, expressed as a percentage. Higher efficiency means less wasted energy. |
Power Supply Form Factors
ATX (Advanced Technology Extended) |
The most common form factor for desktop PCs. Standard size and mounting configuration. |
SFX (Small Form Factor) |
Smaller form factor used in compact PCs. Often found in Mini-ITX builds. |
TFX (Thin Form Factor) |
Slim form factor designed for low-profile cases and small systems. |
EPS (Entry-Level Power Supply Specification) |
Primarily used in servers and high-end workstations. Provides more power and additional connectors. |
Key Voltages and Rails
+12V Rail |
Supplies power to the CPU, GPU, and some storage devices. Critical for modern PCs. |
+5V Rail |
Powers USB ports, older components, and some SSDs. |
+3.3V Rail |
Supplies power to RAM, motherboard chipset, and some SSDs. |
-12V Rail |
Used by older serial ports and some legacy components. Less critical in modern systems. |
+5Vsb (Standby) |
Provides power to the motherboard for standby functions, such as wake-on-LAN and USB charging when the system is off. |
Selecting the Right Power Supply
Wattage Calculation
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Efficiency Certifications (80 Plus)
80 Plus certifications guarantee a certain level of efficiency at different load percentages (20%, 50%, and 100%). Higher certifications indicate better efficiency and less wasted energy.
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Modular vs. Non-Modular
Non-Modular |
Cables are permanently attached to the PSU. More affordable but can lead to cable clutter. |
Semi-Modular |
Some cables are fixed, while others can be detached. Offers a balance between cost and cable management. |
Fully-Modular |
All cables can be detached, allowing for maximum customization and clean cable management. Generally more expensive. |
Connectors and Pinouts
Common Connectors
24-pin ATX Connector |
Main connector for the motherboard, supplying power to most components. |
4/8-pin CPU Power Connector (EPS 12V) |
Supplies dedicated power to the CPU. High-end motherboards often use an 8-pin connector or an 8+4 pin combination. |
6/8-pin PCIe Connector |
Provides power to the graphics card. Higher-end GPUs may require two 8-pin connectors. |
SATA Power Connector |
Powers SATA-based storage devices (SSDs, HDDs) and some optical drives. |
Molex Connector |
Older connector type used for some fans, peripherals, and older hard drives. Less common in modern systems. |
Floppy Connector (Berg Connector) |
Used to power floppy drives. Rarely used in modern systems. |
Pinout Basics (ATX 24-pin)
Understanding the ATX 24-pin connector pinout helps in troubleshooting and custom builds. Here are some key pins:
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Troubleshooting and Maintenance
Common Issues
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Testing a Power Supply
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Maintenance Tips
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