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Seasonic Prime 850 W Titanium PSU Review

Seasonic made an impressive entry in the 80 PLUS Titanium category with its Prime series. This line's current flagship, offering 850W capacity, is being reviewed today. Besides high efficiency, it sports quiet operation and top performance.

Load Regulation, Hold-Up Time, And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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The 850W model's hold-up time is lower than Seasonic's Prime 650 W, but it still smokes the competition.

Inrush Current

For details on our inrush current testing, please click here.

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The inrush current with 115V input is normal. But it's a little higher than expected with 230V.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.1A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails. 

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan SpeedFan NoiseTemps (In/Out)PF/AC Volts
15.206A1.985A1.974A0.995A84.7392.18%440 RPM20.7 dB(A)38.67°C0.968
12.130V5.041V3.341V5.005V91.9241.04°C115.1V
211.444A2.970A2.961A1.200A169.6193.87%440 RPM20.7 dB(A)38.86°C0.991
12.125V5.039V3.340V4.998V180.6941.35°C115.1V
318.043A3.478A3.472A1.400A254.8194.12%440 RPM20.7 dB(A)39.48°C0.996
12.122V5.036V3.338V4.990V270.7342.51°C115.1V
424.629A3.974A3.954A1.605A339.7093.67%440 RPM20.7 dB(A)40.60°C0.993
12.120V5.035V3.335V4.982V362.6643.86°C115.1V
530.874A4.969A4.946A1.805A424.6293.29%450 RPM21.0 dB(A)41.37°C0.992
12.118V5.034V3.334V4.975V455.1544.18°C115.1V
637.126A5.961A5.939A2.009A509.5892.71%530 RPM23.6 dB(A)42.15°C0.994
12.116V5.032V3.332V4.968V549.6645.22°C115.1V
743.380A6.959A6.931A2.214A594.5192.18%410 RPM19.5 dB(A)43.00°C0.995
12.112V5.032V3.332V4.960V644.9447.34°C115.1V
849.638A7.949A7.922A2.420A679.4891.49%520 RPM23.4 dB(A)44.40°C0.996
12.110V5.031V3.331V4.953V742.6748.87°C115.1V
956.324A8.455A8.440A2.420A764.5790.76%620 RPM27.6 dB(A)45.44°C0.997
12.108V5.029V3.329V4.950V842.4250.37°C115.1V
1062.760A8.957A8.927A3.042A849.3090.08%975 RPM37.9 dB(A)46.64°C0.997
12.103V5.027V3.327V4.927V942.8551.93°C115.1V
1169.828A8.965A8.934A3.049A934.3389.31%1305 RPM47.6 dB(A)46.84°C0.997
12.096V5.021V3.323V4.917V1046.2152.68°C115.1V
CL10.098A12.011A12.005A0.004A102.8489.58%440 RPM20.7 dB(A)45.28°C0.980
12.139V5.082V3.381V5.089V114.8050.51°C115.2V
CL269.946A1.003A1.003A1.001A859.4390.33%975 RPM37.9 dB(A)46.44°C0.997
12.097V4.997V3.300V4.964V951.4452.04°C115.1V

Load regulation is tight on all major rails, just like Seasonic promises. In addition, the output noise stays low despite the tough conditions we test under. It's only during the overload test, when we push the PSU beyond its official specs, that the noise reaches 48 dB(A).

Under 10% and 20% loads, this PSU easily meets the corresponding 80 PLUS Titanium levels. Although that's not the case with 50% load, we should stress that our tests are more taxing than the 80 PLUS organization's. Finally, under full load and despite the almost 47°C operating environment, Seasonic's SSR-850TD passes the 90% mark. It is also worth mentioning that the 94% efficiency level is met during the 30% load test. This is one of the most efficient PSUs we have evaluated so far.

Aris Mpitziopoulos
Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.