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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.

Transient Response Tests

Advanced Transient Response Tests

For details on our transient response testing, please click here.

Ιn these tests, we monitor the SSR-850TD's response in two different scenarios. First, a transient load (10A at +12V, 5A at 5V, 5A at 3.3V, and 0.5A at 5VSB) is applied for 200ms while the PSU works at 20 percent load. In the second scenario, Seasonic's 850W Prime is hit by the same transient load while operating at 50 percent load. In both tests, we use our oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.

These tests are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100 percent load of CPU/GPUs). We call these tests "Advanced Transient Response Tests," and they are designed to be very tough to master, especially for a PSU with a capacity of less than 500W.  

Advanced Transient Response at 20 Percent

VoltageBeforeAfterChangePass/Fail
12V12.130V12.039V0.75%Pass
5V5.040V4.947V1.85%Pass
3.3V3.341V3.189V4.55%Pass
5VSB4.999V4.957V0.84%Pass

Advanced Transient Response at 50 Percent

VoltageBeforeAfterChangePass/Fail
12V12.118V12.039V0.65%Pass
5V5.033V4.940V1.85%Pass
3.3V3.334V3.180V4.62%Pass
5VSB4.973V4.934V0.78%Pass
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The transient response of the +12V rail is good enough, though we'd like to see closer to 0.5% in both tests. The 5V and 5VSB rails do pretty well. However, the 3.3V rail needs more work in order to keep its deviations below 3%.

Here are the oscilloscope screenshots we took during Advanced Transient Response Testing:

Transient Response At 20 Percent Load

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Transient Response At 50 Percent Load

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Turn-On Transient Tests

In the next set of tests, we measured the response of the PSU in simpler transient load scenarios—during its power-on phase.

For the first measurement, we turned off the SSR-850TD, dialed in the maximum current its 5VSB rail could output, and switched the PSU back on. In the second test, we dialed the maximum load the +12V rail could handle and started the 850W Prime while it was in standby mode. In the last test, while the PSU was completely switched off, we dialed the maximum load the +12V rail could handle before switching it back on from the loader and restoring power. The ATX specification states that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2V, and 5.5V for 5V).    

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We observe a small voltage overshoot at 5VSB, along with some waves and not-so-rough spikes in the next two tests. Overall, Seasonic's performance is good, though not perfect.

  • trampus123
    I want one
    Reply
  • Nintendork
    There's no need for CF/SLI anymore, the typical PC + RX480/1080 class gpu barely goes above 300w (even less with APU setups or RX460/1050ti). We need way more 400-500w Titanium PSU's.

    We should have 90% efficiency at 50w load with PSU's in that wattage range.
    Reply
  • WFang
    I'm eagerly anticipating the 600W Passive Seasonic Titanium unit.. I read about it almost a year ago, and still have not seen it tested here ... hope that changes soon.
    Reply
  • LordDrk
    Paid $179 for my EVGA 1000W T2 on ebay =p
    Reply
  • mlga91
    Im not worthy of this one.
    Reply
  • Unolocogringo
    18846027 said:
    There's no need for CF/SLI anymore, the typical PC + RX480/1080 class gpu barely goes above 300w (even less with APU setups or RX460/1050ti). We need way more 400-500w Titanium PSU's.

    We should have 90% efficiency at 50w load with PSU's in that wattage range.

    Just because you do not need one , does not mean others don't.

    I run multiple graphics cards for Folding@Home.The more you can run on each CPU the better. People who run Dual 1080s or dual 39x cards need them to push their 4K monitors.
    So there is a need for them.

    Reply
  • TJ Hooker
    Nintendork said:
    We need way more 400-500w Titanium PSU's.
    We should have 90% efficiency at 50w load with PSU's in that wattage range.
    The thing is, efficiency arguably matters less the lower the power is, because the absolute power being wasted is small. A 500W titanium PSU at max load is only drawing 15W more than a gold rated one. At 50%, 10W. As load drops past 50%, efficiency goes down, but absolute power wasted will still likely go down as well. I don't know, getting a 400W titanium PSU just seems like you're probably paying a lot more money than is necessary for a over engineered PSU which has little to no difference in performance compared to a less efficient, cheaper PSU.
    Reply
  • JV_
    No recommendation award for this one?
    Reply
  • powernod
    Just like Aris stated at his review, i find it amazing how Seasonic managed to generate such a low ripple values without using cable-in capacitors like the rest of the companies do !!
    Reply
  • Aris_Mp
    it has an editor's choice. It will be soon added :)
    Reply