5-way High-End 1KW+ PSU Round-Up
Test Results - Voltages
Test Results - Voltages
When examining the performance of a PSU under load it is often all too easy to get tied up in the output voltages rather than how stable the unit actually is. For example: PSU 'A' might have an idle voltage reading of 12.2v and a load reading of 11.9v whereas PSU 'B' might output 12.0v at idle and 11.8v under load. Common sense would tell us to opt for PSU 'A' as under load it outputs the voltage closest to our ideal +12.0v. However, while this is most certainly carries some weight. PSU 'B' actually exhibited less fluctuation between idle and load voltages, indicating that it is better equipped at coping with the stress of a heavy load.
For this reason, when viewing the graphs below we will not only be assessing the how close the voltages are to +12.0v under load, but also how flat the line is between 50% and 100% load depicting the stability of the unit.
Starting off with the +3.3v rail both the Cooler Master and Corsair units manage the least fluctuation between 50% and 100% load voltages. However, for some reason the Corsair unit seems to have its +3.3v rail voltages set a lot lower than the rest of the units in the test, with voltages as low as 3.2v being produced under full load.
The Be-Quiet and Silverstone units show the greatest dip in 50% and 100% load voltages, indicating that their +3.3v rails aren't quite as strong as the rest of the PSU's in this test.
Moving on to the +5v rail we can see that most of the results run in an almost parallel downward fashion. However, the Enermax unit doesn't seem to take kindly to the increase in load from 75% to 100% with the voltage dipping from 4.96v to 4.89v. Of course, this is still well within specification, but its certainly not as strong as the other units.
In the +12v1 and +12v2 results the most stable units are the Enermax and Silverstone, with both exhibiting little change in voltages from 50% load to 100% load. The unit with the largest visible fluctuation between light and heavy load is Corsair unit, which produced a flat line between 50% to 75% loads and then takes a rather sharp downward slope once 100% load is applied.
At the bottom of the chart is the Be-Quiet unit, which starts at a fairly reasonable 11.9v under 50% load, but then takes a fairly large drop down to 11.77v which would probably send the overclockers among us running for the hills.
On to the +12v3 and +12v4 rails and we are dwindled down to four contestants. Once again the Be-Quiet unit is sitting at the bottom of the pack with voltages as low as 11.68v under 100% load, while at the other end of the scale, the Cooler Master and Enermax exhibit the least voltage fluctuation overall.
Despite the fact that both the Enermax and the Silverstone unit are spec'ed as having six (albeit virtual) +12v rails, Enermax's Chroma 6310 only allowed for testing on four of these rails. However, both the Be-Quiet and Cooler Master units that were sent to Germany for testing on a Chroma 6000 had loads applied to each of their six rails.
As we can see from above, the Cooler Master unit produced the more stable voltages of the two units with a slightly straighter line between 50%, 75% and 100% loads. Once again the voltage output of the Be-Quiet unit under 100% load was very low, coming in 0.20v below the Cooler Master.
While not as important as the primary +3.3v, +5v and +12v rails in a PSU, the+5vsb rail is responsible for providing power to components such as USB Input Devices and Network cards while the PC is in standby mode. PSU's failing to provide enough voltage to this rail could prevent devices such as USB keyboards from functioning and allowing the system to be resumed from standby with a keypress.
As we can see from the chart above, the Corsair and Silverstone units provide the most stable voltages here between 50% and 100% load levels, with other units experiencing slight fluctuations (exaggerated by the graphs scale), but certainly nothing to worry about.
Negative voltage rails such as the -12v and -5v rails were introduced back on the original IBM PC standard PSU's and have decreased in terms of viable usage over the years. As a result the -5v rail was recently dropped from the latest PSU's when the ATX 2.01 standard was introduced. However -12v remains, and despite its questionable usefulness the above graph shows how each PSU performed when a small load was applied to this rail.
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