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?

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Load Testing

For those of you that are curious as to some of the reasoning and equipment behind our PSU testing program here at HardOCP, we have put together a living document that shares a lot of the behind the scenes of the program. The testing we are conducting today is exactly as described in that document and will begin with a range of loads tested at 120v input including our torture test and then move on to the same set of tests at 100v input but without the torture test.

120v Load Testing Results

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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 results of Test #1 show the main positive DC output rails starting off above nominal. The efficiency for this unit is starting off today at an excellent value of 93.48% and an exhaust temperature of 48C.

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 almost no changes in DC output voltages relative to what we saw with Test #1. Indeed, the only change we see that matters is the 0.01v drop on the 3.3v rail. The efficiency has moved up slightly to 94.09% while the exhaust temperature has moved up to 53C.

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, 5v, and the 3.3v rails staying even with the values we saw in Test #2. The efficiency in Test #3 moves down to 91.67% while the exhaust temperature has risen to 57C.

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 the largest change of testing on our main DC output voltages as the 12v rail rises by 0.02v. The minor rails, however, stay even with the values they were posting in Test #3. The efficiency has dropped a bit in this test as we see it at 90.05% and the exhaust temperature is 60C.

Load Testing Summary

Previously, we reviewed the PRIME 750W from Seasonic and that unit just killed the competition. I mean, killed the competition. So, what did the PRIME 850W do today? Well, it killed the competition and then went back and killed them again just to make sure they were dead. How so you might ask? Well, I'm glad you asked that because it was glorious. By the numbers, the PRIME 850W had peak changes of 0.02v on the 12v rail, 0.00v on the 5v rail, and 0.01v on the 3.3v rail. Those numbers are not just OUTSTANDING but the total change was 0.03v and that TOTAL change is similar to what we saw from just one rail on the PRIME 750W. Beyond that, these results were so embarrassingly good that there are no 850W units we have seen (or even on the market currently that we are aware of) that hit this kind of result. From the now positively ancient Corsair HX850 to the Antec HCP-850 Platinum to the Seasonic X-850 to the whatever, the PRIME 850W beats them all. What this means is that the only comparable product we have seen is the PRIME 750W but it is 100W smaller in capacity and it doesn't do quite as well as the PRIME 850W! When we move on to the efficiency side of things, we see that the PRIME 850W ranged from 90.05% to 94.09% efficient which is outstanding. Lastly, the exhaust temperature peaked at 60C. With the PRIME 750W we said it was "starting off in a class all its own," with the PRIME 850W it is doing that and then some. Let’s move on to the 100v testing and see how the unit does there.