Seasonic Flagship PRIME 850W Power Supply Review

Seasonic is one of our long-time favorites when it comes to high power and high efficiency desktop computer power supplies. Seasonic does not introduce wave after wave of new PSU series, so when it does come across with a new platform it gets our attention. Is the TITANIUM rated PRIME 850W worthy of yours?

continued...

Ripple Testing

Since voltage output is not the only concern when it comes to quality DC output we next examined the ripple and regulation characteristics of the PRIME 850W. We examine these points since unnecessary ripple can cause premature failure of sensitive components in a number of different PC subsystems.

The DC output quality was logged via our digital oscilloscope and the EasyScope II software package. Each divider horizontally represents 2ms while each divider vertically represents 0.05v or 50mv. The ATX specification states that a unit should remain at or below 120mV of ripple and noise on the 12v rail while under 50mV on the 3.3v/5v rails.

Control Test Graphing

Article Image

This image is the blank background control test on an unused connector from our SM-8800 during the PRIME 850W. This lets us determine what the background noise looks like during testing. If at any time a trace deviates from this reading that is the noise/ripple being logged by the oscilloscope for that rail. As you can see the trace is flat and shows as a blue line obscuring the axis. If during a test the axis becomes visible but a waveform is hard to discern it is most likely due to the amplitude of the trace being small in relation to our voltage divider.

120v and 100v Input

Article Image Article Image

Test #1 is equal to approximately 25% of the rated capacity of the PRIME 850W at 45c. This makes Test #1 equal to 223W by loading the 12v rail to 16a, the 5v rail to 2a, the 3.3v rail to 1a, the +5vsb to 2a, and the -12v to 0.3a. The PRIME 850W is starting off quiet with all of the rails peaking at ~10mV of ripple/noise or less.

Article Image Article Image

Test #2 is equal to approximately 50% of the rated capacity of the PRIME 850W at 45c. This makes Test #2 equal to 433W by loading the 12v rail to 32a, the 5v rail to 4a, the 3.3v rail to 3a, the +5vsb to 2a, and the -12v to 0.3a. Test #2 sees a bit of a change compared to what we saw in Test #1 as the 12v rail, which had been hitting 10mV of ripple/noise, has dropped back below that threshold along with the other rails.

Article Image Article Image

Test #3 is equal to approximately 75% of the rated capacity of PRIME 850W at 45c. This makes Test #3 equal to 641W by loading the 12v rail to 48a, the 5v rail to 6a, the 3.3v rail to 4a, the +5vsb to 2a, and the -12v to 0.3a. Test #3 sees the 12v rail peak at less than ~10mV of ripple/noise while the minor rails are both coming in at less than ~10mV of ripple/noise once more.

Article Image Article Image

Test #4 is equal to approximately 100% of the rated capacity of the PRIME 850W at 45c. This makes Test #4 equal to 859W by loading the 12v rail to 68a, the 5v rail to 2a, the 3.3v rail to 2a, the +5vsb to 2a, and the -12v to 0.3a. In the final regular test, we see all of our main DC output rails holding the line at less than ~10mV of ripple/noise.

Torture Test

Article Image

The Torture Test is equal to approximately 80% of the rated capacity of the PRIME 850W at 45C. This makes the Torture Test equal to 674W by loading the 12v rail to 50a, the 5v rail to 7a, the 3.3v rail to 5a, the +5vsb to 2a, and the -12v to 0.3a. At the end of the Torture Test, we see the 12v rail has peaked at ~10mV of ripple/noise and the minor rails have once more stayed below ~10mV of ripple/noise.

DC Output Quality Summary

The overall DC Output Quality of the PRIME 850W is perhaps tied with being the best aspect of this unit today when it comes to performance metrics. With the DC Output Quality, the PRIME 850W is not only doing amazingly well it IS besting the PRIME 750W. Not only that, it is besting just about every unit we have seen to date regards of capacity and that title used to belong to the PRIME 750W! So, how does this unit outpace the PRIME 750W then? Well, there wasn't much room but with the 12v rail peaking at just ~10mV of ripple/noise compared to ~15mV with the PRIME 750W (and less than ~10mV on the 5v and 3.3v rails again) this unit just barely slides ahead of the PRIME 750W. So, in the end, this unit is just smoking the competition except for the PRIME 750W which it is still better than. This is truly outstanding! Let's move on and see how all of this wraps up!