Result Summary

The FSP VITA GM 850 W passed our tests with no issues, delivering 100 and 110 % of its rated power in high ambient temperatures.

The fan performance deserves a separate paragraph. As expected, the fan spun up right from the first tests, yet the speed was a bit higher than FSP's charts at around 600 RPM. However, the fan curve overall looked very much like the one presented by FSP with no significant rise in RPMs until we reached 70 % load. During the final three tests we also exceeded the 1000 RPM limit. When translated into noise metrics, the results are a quite good. For the first two thirds of the tests the VITA GM 850 W remains barely audible. As the fan ramps up quite steeply so does the dBA readings. However, even in high ambient temperatures at full load we maintain a sub-40 dBA level. At the overload test we surpass this value significantly as the noise increases, but overall that's an admirable performance.

What looks less impressive is the power factor results at low loads and the overall regulation on the minor rails, but more on that in the voltage regulation section.



The VITA's achieved efficiency is well within the 80 Plus Gold standard. Efficiency at 5 and 10 % are adequate but nothing to write home about. But at 20 % the unit already achieves a >92 % efficiency—in line with the requirements for a Platinum rating. However, the efficiency does not rise that significantly higher over the other tests, reaching 93.1 % at the peak and falls down to just over 90 % at the full power test. Again, nothing to complain about.

Voltage Regulation

While the performance of the +12V rail is very good, both minor rails could have tighter regulation, especially at the highest loads, approaching 2.5 % at 100 % load. Of course, that's still very much within the ATX specification.

Ripple

Ideally you want the DC voltage delivered by your power supply to be a completely flat line when looking through an oscilloscope. However, due to the switching nature of ATX power supplies and the less than ideal real world behavior of all the components involved, we get very small fluctuations in output voltage known as ripple and noise. The ATX spec allows for ripple of up to 120 mV for the +12 V rail and 50 mV for the minor rails.


Ripple control on the PSU looks very good overall being well under the ATX requirements even when going beyond the maximum rated power output. The oscilloscope waveform output of the 110% load test can be seen below.

Short Circuit Protection

Short circuit protection is one of the most fundamental and important protections for a power supply. If a short circuit is detected on any rails, the PSU should turn off to prevent damage to itself and other components.


SCP worked as expected with the unit.