Power Supply FAQ (Frequently Asked Questions)

• Power Supply Basics
  • What is a "power supply"?
  • How do I know how big of a power supply I need?
  • Is there such a thing as "too much power"?
• How power supplies are rated
  • What is the "wattage" number actually telling me?
  • What is the difference between "continuous" and "peak" ratings?
  • How does the temperature inside of my case affect the performance of my power supply?
  • Is the MTBF temperature an indication of what temperature the power supply's output rating is measured at?
• Questions about power supply efficiency
  • What is “efficiency”?
  • Why is efficiency important?
  • Aren't higher wattage units are less efficient at lower loads?
• Questions about active power factor correction (PFC)
  • What is "power factor"?
  • So what if I have a poor power factor?
  • What is power factor correction?
• Using a computer power supply around the world
  • Different countries have different input voltages
  • My power supply doesn't seem to support my country's voltage
  • Different countries have different plug types
• The different connectors of a computer power supply
  • The 20+4, or 24-pin, main power connector
  • The 4+4-pin, or 8-pin, CPU power connector
  • The 6+2-pin, or 8-pin, PCIe power connector
• Power Supplies With Multiple +12V Rails
  • What are "multiple +12V rails"
  • Why split up the +12V rail?
  • Is it true that some PSU's that claim to be multiple +12V rails don't have the +12V rail split at all?
  • In the past, I've been told that splitting the +12V rails provide "cleaner and more stable voltages"
  • Some people claim they can overclock better, etc. with a single +12V rail PSU
• Basic power supply troubleshooting
  
  • My power supply doesn't turn on
  • Voltage readings using the BIOS or software programs
  • My -12V, -5V, etc. show voltages that are way out of specification
  • Using a multi-meter to check voltages
  • Using a multi-meter to determine voltage regulation