Seasonic Platinum SS-1200XP3 Hot Test Results

Surprisingly, even though they are both based on the exact same platform, the power quality of the Seasonic Platinum SS-1200XP3 is better than that of the less powerful 1050W model. It is not a very large difference, but it is evident. Whether this is true of all the 1200W models vs. the 1050W models is impossible to say, as there is always some small variance between individual units, but it is interesting to note nonetheless. The maximum voltage ripple that our instrumentation recorded is 40mV under maximum load, while siphoning 85.26 Amperes from the 12V line. Voltage regulation is a little better as well, at 0.71%, 0.82% and 0.95% for the 3.3V, 5V and 12V lines, respectively.

Main Output
Load (Watts) 242.86 W 604.83 W 905.43 W 1202.76 W
Load (Percent) 20.24% 50.4% 75.45% 100.23%
Line Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 4.26 3.36 10.66 3.35 15.99 3.33 21.31 3.33
5 V 4.26 5.1 10.66 5.08 15.99 5.07 21.31 5.06
12 V 17.05 12.13 42.63 12.08 63.94 12.06 85.26 12.01


Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
3.3V + 5V
3.3V 0.7% 14 16 18 18 14 20
5V 0.82% 14 18 22 24 16 24
12V 0.95% 16 26 32 40 36 18

High ambient temperature has a discernible impact on the efficiency and performance of the Seasonic Platinum SS-1200XP3 as well, but not as large an impact as it did with the 1050W model. The average nominal load (20-100%) efficiency is reduced by 0.4%, with the maximum efficiency being 93.8% at 50% load. Apparently, the higher ratings of the components used to create the Platinum SS-1200XP3 are a bit more resilient to heat than those of the 1050W model.

The thermal and noise test results of the Seasonic Platinum SS-1200XP3 inside our hotbox were unsurprising, displaying similar behavior to that of the 1050W model. The cooling fan once again starts at 20% load but this time the Platinum SS-1200XP3 does not remain silent for long, as the cooling system reacts aggressively to the increasing temperatures, rapidly increasing the speed of the fan. This way the Platinum SS-1200XP3 maintains very low operating temperatures for a 1200W unit, effectively increasing its long-term reliability, but it sacrifices acoustic comfort in the process.

Seasonic Platinum SS-1200XP3 Cold Test Results Conclusion


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  • ijozic - Thursday, September 4, 2014 - link

    It sounds like it would cost noticeably more for something most people PROBABLY won't really care about. And the market is already quite competitive.. Reply
  • Samus - Thursday, September 4, 2014 - link

    The only complicated factor is space inside the standard ATX housing, but considering there are 500-watt 80+ Gold SFX PSU's that are 1/3rd the size of ATX, making a 100-watt primary stage with a 1000-watt secondary stage shouldn't be impossible. The most expensive part would likely be the cap for the relay (1/4 farad) and obviously that cap is going to be pretty large, most electrolytic caps this size are around 5" long.

    I think the BOM would be ~$20, and engineering it in isn't rocket science. This could totally be done, and if I were paying $200+ for a PSU, I'd expect some level of engineering beyond a good bridge design and PFC.
  • jann5s - Thursday, September 4, 2014 - link

    have a look at the pico-PSU, these go up to 160W and are approximately the size of the ATX-plug attached to the umbilical coard of your PSU, this will definately fit. Reply
  • DanNeely - Thursday, September 4, 2014 - link

    With a picoPSU you need to look at not just the 12V to 3.3/5V (smaller models) or 19V to 12/5/3.3V circuitry on the ATX plug; but the size of the external power brick used to feed it. It's still probably feasible volumetrically, but isn't nearly as much of a gimmie as just looking at the size of the ATX plug module implies. Reply
  • DanNeely - Thursday, September 4, 2014 - link

    ... especially since this could potentially be done by beefing up the existing Vsb circuit instead of adding something entirely new. JonnyGuru's testing shows current Vsb implementations aren't particularly impressive at only around 80%; but depending on how much worse current models perform below 10% some gains might still be reasonable. With the Titanium spec mandating 90% efficiency at 10% load though I'm not sure it's really worth it. On the 300-700W units that are suitable for ~90% of enthusiast systems 10% of rated power is generally enough to cover idle loads as long as you don't do anything silly (eg running an IGP powered low power mITX board with an SLI capable PSU). OTOH idle loads are steadily improving with each new CPU/GPU generation and the 80+ group will need to extend the standard to be tougher somewhere for whatever comes after titanium. Reply
  • TelstarTOS - Thursday, September 4, 2014 - link

    I totally agree. What's holding me to get a 1000W+ PSU is the efficiency at low loads. With CPUs getting more and more green, PSUs should do the same and not only when under full load (which is a countersense if you really think about it). Reply
  • DanNeely - Thursday, September 4, 2014 - link

    More attention is being paid to lower end efficiency than in the past; and this PSU is a prime example. While it falls short of the (new) 90% efficient at 10% load requirement for 80+ titantium, it's ~89% efficiency is much better than any of the other PSUs reviewed earlier this year did; none of which did better than the low to mid 80's at that level. Reply
  • Phillip Wager - Monday, September 8, 2014 - link

    i like the dual stage idea but i am assuming most consumers are not willing to pay more for additional cost/complexity because that small amount of power that you are wasting turns out to be a very small amount of money over the lifetime of the system. I am somewhat suprised with your test results with your system because my computer has nearly identical specs and i have a 600 watt power supply and i have never had so much as a hiccup. Maybe get a different device for measuring power draw or perhaps your power supply is not as inefficient as you think. Reply
  • bsim500 - Thursday, September 4, 2014 - link

    I agree, but there's not much you can do. It's the nature of high-wattage PSU's. If they came out with a 95% efficient "super platinum" PSU, lower wattage PSU's would adopt the same technology and the "idle gap" would still remain.

    Personally, I have a Seasonic G360 (yes, 360W PSU) that perfectly feeds an i5 + 7870 GFX card, and pulls (measured at the wall) : 182w peak Prime + Furmark / 110-150w typical gaming load / 88w 4T Prime or X264 encode load (CPU only) and 37w idle (which falls to 26w if discrete GFX card is removed, and that's with 1600MHz Ivy Bridge idle, not 800MHz Haswell), never pulling more than 50% PSU draw even under combined synthetic CPU+GPU "power viruses", and spending 90% of its time at +90% PSU efficiency with a virtually silent fan.

    That 26-37w idle wattage on these PSU's is barely 50-60% efficiency level, yet the number of people who "swear" they "need" a 1200w PSU just for a single mid-range dGPU gaming rig is quite comical. ;-)
  • Samus - Thursday, September 4, 2014 - link

    I know, "right sizing' a PSU is something few people understand. The worst thing you could do to your wallet is spend a fortune on a 600+ watt PSU and spend another fortune paying for it to inefficiently idle over the years for that i5 with integrated graphics and a single hard disk... Reply

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