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Seasonic M12II-500 500W Modular ATX12V v2.2 Desktop Power Supply

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Seasonic M12II Power Supply

Seasonic M12II Power Supply


The Bottom Line

If you are looking to put together a desktop PC system that runs very quiet, is energy efficient and has flexible cable usage without have to get a high wattage unit, Seasonic has the answer for you with the M12II-500 unit. The only real drawback is that it is a fairly expensive unit that may be more than some of willing to spend.
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  • Extremely Low Noise Operation
  • Very Stable Voltages
  • High Efficiency Rating


  • Fairly Expensive
  • Primary Power Cables May Be Too Short For Some Tall Tower Cases


  • ATX12V Version 2.2 Compliant with 20/24-pin Primary and 4 and 8-pin 12V Power Connector
  • 500W Combined Load Output (420W Maximum on Dual 12-Volt Rails)
  • PCI-Express 6+2-pin and 6-pin Modular Power Connectors
  • Modular Power Connectors with 6 SATA, 8 4-pin Molex and a Dual Floppy Connector Adapter
  • Single 120mm Ball Bearing Cooling Fan with Thermal Speed Control
  • 80Plus Efficiency Certified
  • >100,000 Hour MTBF
  • Five Year Warranty

Guide Review - Seasonic M12II-500 500W Modular ATX12V v2.2 Desktop Power Supply

5/13/08 - The Seasonic M12II-500 is a 500W model that uses the ATX12V version 2.2 specs. This allows the unit to be used in a wide range of new and older desktop or workstation platforms. While the system is modular, the primary power cables are fixed. The cable lengths are generally good for most mid to small tower designs but larger full tower cases may require extensions to fully reach.

The M12II-500 offers a variety of connector options for use inside of the desktop system. There are a total of 7 power connectors on the power supply. Two are specific to the PCI-Express graphics while the others can be used for the SATA or Molex power connectors. The cables supplied provide a total of six SATA and eight 4-pin molex connectors. An additional adapter is supplied to convert a standard 4-pin molex into two 4-pin floppy connectors. PCI-Express cables provide one 6+2 connector for use with 6 or 8-inch cards and a 6-pin for the other. All cables are sleeved.

During testing of the M12II-500, the unit provided very stable voltages. The 12V lines tended to run a little high with about .1 volts higher while the 5V and 3.3V lines running a bit low at 4.94V and 3.22V respectively. Overall this is extremely close and well within the ATX specifications. The unit did not run very hot and the 120mm fan did an excellent job of cooling of the unit without making much noise. It is likely other case fans will be louder than this power supply.

Even though all the packages and materials have on it a three year warranty, Seasonic actually provides a five year warranty on the model and includes a special insert inside the retail package to let users know of this.

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