Articles: Cases/PSU
 

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Cables and Connectors

The PSU is equipped with the following cables and connectors:

  • Mainboard cable with a 20+4-pin connector (53 cm)
  • CPU cable with a 4+4-pin connector (52 cm)
  • CPU cable with an 8-pin connector (52 cm)
  • Two connectors for graphics card cables
  • Five connectors for peripheral power cables

Included with the PSU are:

  • One graphics card cable with one 6-pin connector (56 cm)
  • One graphics card cable with one 6+2-pin connector (56 cm)
  • Two cables with three PATA power connectors on each (46+16+16 cm)
  • Three cables with three SATA power connectors on each (45+14+14 cm)

The selection of cables is standard enough. It is good that there are a lot of SATA connectors but I don’t like the 52cm CPU power cable which is going to be too short in many system cases with a bottom PSU compartment. I would request all PSU manufacturers to provide a 60cm or longer CPU cable even at the expense of the second CPU cable which is necessary but for a few users.

Compatibility with UPSes

Like the S12-II 520, this PSU refused to work normally with my UPS. It was stable at loads up to 350 watts when powered by the mains but did not work after switching to the batteries.

Thus, I can suppose that the high-wattage S12-II and M12-II series models have a different active PFC design than the low-wattage models and cannot work normally with UPSes that have non-sinusoid output voltage. The S12-II 430, having a somewhat different interior design than the S12-II 520 and M12-II 620, had no problems working with my UPS.

Output Voltage Stability

The M12-II cannot match PSUs with dedicated voltage regulation in terms of output voltage stability, but it is good enough for its product class. The voltages deflect no more than 3% in the typical load range.

Output Voltage Ripple

The output voltage ripple is low and can only be seen clear enough on the +3.3V rail. There are but occasional spikes of voltage on the other rails.

Noise

This PSU is cooled by an ADDA AD1212HB-A71GL fan which is rated for 2200 RPM. This is about 10% faster than in the above-discussed PSUs of lower wattages.

However, the fan starts out at a speed of only 500 RPM and keeps it for a while at higher loads. Then, it accelerates to 1000 RPM at 300 watts (this is the top limit of silent operation; even an undemanding user will hear the fan at a higher speed) and becomes downright noisy at 400 watts. The PSU produces a powerful din at full load.

Thus, like the above-discussed S12-II series models, the M12-II is very quiet at low loads but loud at 300 watts and higher. The only advantage over the lower-wattage S12-II 520 is that the latter’s fan begins to accelerate sooner.

Efficiency and Power Factor

The PSU is 85% and more efficient through the largest part of the load range.

Standby Source

The standby source copes with its job just fine.

Summary

The M12-II differs from the S12-II series in having modular cables and a slightly longer case. It is a well-made, highly efficient PSU which is also very quiet at low loads. The downside is that its output voltages are not absolutely stable, its noise quickly grows up at loads above 300 watts, and it is incompatible with UPSes with non-sinusoid output voltage.

Thus, there is no reason to prefer a higher-wattage model in the S12-II or M12-II series if you want to have a quieter PSU. All of them are quiet at loads up to 300 watts, which is less than 50% of their max output power. So, if your computer has an average power draw of 200 watts or lower (this is a rather typical gaming computer with a dual-core processor and a Radeon HD 5850 graphics card), each of these three models will be a good choice for it. But if you’ve got a more advanced configuration, you may want to consider other PSUs in which the fan does not accelerate as fast as in the S12-II and M12-II.

 
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