Articles: Cases/PSU
 

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Specifications

The specifications improve as we move up the series. The junior model can only deliver 423 out of its full 500 watts via the +12V rail whereas the midrange model’s 540 out of 600 watts is much better both in absolute (there’s 60 rather than 68 watts left for the less used power rails) and relative (the +12V rail can deliver 90% rather than 86.4% of the PSU’s full output power) numbers. The senior model offers the best specs, of course. It can yield 660 out of its full 700 watts via the +12V rail and its efficiency is 88% as opposed to the other models’ 86%.

Like the above-discussed Chieftec, the Cooler Master PSUs are only designed for 230V mains.

UPS Compatibility

Working together with our APC SmartUPS SC 620, the RS-500-ASAB was stable at loads up to 354 watts when powered by the mains. Its 600W and 700W cousins were stable at up to 362 and 392 watts, respectively. None of them could switch to the UPS’s batteries even at a load of 290 watts, though.

Cross-Load Voltage Stability

We’ll build our diagrams for each PSU individually for better readability.

This model performs expectedly for a PSU without dedicated voltage regulation. Its +12V voltage goes out of the permissible range when there’s a moderate load on the +12V rail and a high load on the other rails. The +5V voltage is unstable at loads above 80 watts while the individually regulated +3.3V voltage is the most stable of all.

We must note, however, that the voltages are close to the required levels in the typical load range.

The 600W model performs in the same way except that the +5V voltage goes out of the permissible range at higher loads, and the +12V voltage does the same only when the overall load is misbalanced towards the other rails.

The flagship model of the series does much better thanks to its dedicated voltage regulation.

The +12V voltage is just perfect, remaining within 1% of the required level at any load. The +5V voltage is always within 3%, which is good, too. The +3.3V voltage is the least stable of all, going beyond 3% at very low loads. Overall, the RS-700-ASAB delivers very stable voltages.

We must note, however, that each of the Cooler Master PSUs doesn’t work well at minimum loads. When not loaded at all, the +5V rail would trigger protection in the two junior models. And when we lowered the load on the +12V rail from the maximum to the minimum during our test, each model would lose the Power OK signal. We saw the Chieftec CTG-600-80P PSU behave like that, although it was based on a different platform.

Output Voltage Ripple

We’ll show you the results of the models based on different hardware platforms.

The high-frequency voltage ripple of the 600W model is conspicuous on each power rail but is always within the permissible range.

The low-frequency ripple is much weaker.

The 500W model behaved in the same manner as its 600W cousin but its output voltage ripple was weaker overall.

The 700W Cooler Master features a different platform and has stronger voltage ripple on the +5V rail. However, it lacks any voltage spikes on the +12V rail which could be observed with the two junior models.

The low-frequency voltage ripple is weak and can barely be observed on the +12V rail only.

Temperature and Noise

Each of the three Cooler Master PSUs is cooled by a 120mm Globe Fan S1202512L (it’s the same fan as in the above-discussed Chieftec). The only difference is that the impeller is partially covered with a piece of plastic to optimize air flows in the 500W and 600W models. The 700W model has no such feature.

The fan regulation algorithm is the same for each PSU. The fan starts out at a very low speed and maintains it for a long time. Then the fan accelerates steadily until full load.

The 600W model is somewhat worse than its cousins. The start and maximum speed of its fan is somewhat higher and the fan begins to accelerate at a lower load.

The 700W model accelerates its fan later than its cousins. At full load it is in between the 500W and 600W models in terms of noisiness.

Thus, the 500W and 700W Cooler Master PSUs are rather quiet for their wattage. The 600W model is noisier, probably due to the variation in fan specs, which amounts to +/-10% for the Globe Fan S1202512L.

Efficiency and Power Factor

The Cooler Master RS-500-ASAB is 84.6%, 87.3% and 82.6% efficient at the reference loads of 20%, 50% and 100%. The peak efficiency of 87.6% was observed at a load of 260 watts.

The Cooler Master RS-600-ASAB is 86%, 86.3% and 82.4% efficient at the reference loads of 20%, 50% and 100%. The peak efficiency of 87.6% (the same as the junior model’s) was observed at a load of 240 watts.

The Cooler Master RS-700-ASAB is 86.8%, 88.2% and 86.5% efficient at the reference loads of 20%, 50% and 100%. The peak efficiency of 89.1% was observed at a load of 398 watts.

As you can see, the PSUs deliver on the manufacturer’s promise of 86% efficiency for the two junior models and 88% efficiency for the senior model.

The power factor is above 98% with the two junior models, which is normal for PSUs with active PFC. The 700W model is somewhat worse at 97%.

Standby Source

The Cooler Master PSUs are similar in terms of their standby voltage, so we’ll only show you the graph of the junior model:

Of course, the standby source does its job without any problems.

Summary

Cooler Master’s GX-Lite series PSUs are actually quite different among themselves.

The two lower-wattage models are mediocre solutions without special advantages or obvious downsides. Their price is low but they have a lot of competitors in their price range.

The 700W model is more interesting thanks to its dedicated voltage regulation and higher efficiency. It is the cheapest PSU we know of that has dedicated voltage regulation while the rest of its electrical and acoustic parameters are very good, too. Thus, the Cooler Master RS-700-ASAB is quite an attractive option as a high-efficiency PSU for little money.

 
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