External Appearance

The three Seasonic PRIME PSUs that we are reviewing today are almost identical physically, sharing the exact same design and proportions. One can only tell the difference between the models from either the sticker with the electrical specification of the PSU that is found at the top of the chassis, or from the number of connectors at the front side of the units. Do note that the chassis is 170 mm long, which is a bit longer than that of a typical ATX PSU and might be incompatible with some cases, especially ultra-compact designs.

Seasonic is trying to have the PRIME units aesthetically standing out of the crowd mainly by adding chrome parts on the sides and bottom of the chassis. Aesthetics are a subjective matter but we believe that the designer made the PRIME units a bit too shiny, when obviously the concept was to have them looking classy. The sides of the chassis are embossed, with a small vent opening that faces the rear of the unit. These vents are insignificantly small and their direction suggests that they are most likely just decorative elements rather than actual thermal improvements.

The rear side of the PSUs is perforated, with an elongated honeycomb pattern that has been optimized for reduced air drag (i.e. noise). There is a typical on/off switch next to the AC cable connection, and also a push button that turns the hybrid fan mode on or off. With the setting on, the fan will not start until the thermal control circuit defines that it is necessary for the cooling needs of the unit.

The front side of the PSUs are littered with the numerous connectors for their modular cables. Each unit has a different number of connectors that corresponds exactly to the number of cables they come with. The connectors are grouped into three categories; one just for the ATX cable, one for the Molex/SATA cables and one for the PCI-E and CPU cables. All of the PCI-E/CPU connectors are compatible with both of the CPU and PCI-E cables.

650W, 750W, 850W

Internal Design

All three of the units that we are reviewing today are using the same exact fan, the Hong Hua HA13525M12F-Z. It initially appears to be a common 135 mm fan but has a fluid dynamic bearing (FDB) engine, which combines the low noise operation of the sleeve bearing with the longevity of ball bearing engines. The fan has a maximum rotational speed of 1800 RPM.

Seasonic is the designer and a manufacturer that actually also supplies their products to other brands, so there is no hidden OEM behind the PRIME Titanium units, they are entirely of their own design and production. The three PRIME Titanium units that we are reviewing today are also sharing the same exact internal design. As a matter of fact: many of the components are identical, with the only actual difference being the rating of some of the primary components. The heatsinks are identical, as are most of the secondary side capacitors.

The secondary capacitors are either supplied by Nippon Chemi-Con and Nichicon (Solid state), or Nippon Chemi-Con and Rubycon (electrolytic). The filtering stage also is identical between the three units and consists of six Y capacitors, three X capacitors and two filtering inductors. A surge suppressing MOV is also present. All three units are even using the same two primary conversion bridges, which are comically oversized for the power requirements for any of the three units. The two bridges in each of the units could, in theory, handle up to 4.5kW with a mere 90V AC input. Differences occur with the two APFC capacitors at the primary side: the 650W model is using 2×400V/470μF capacitors, the 750W model one uses 400V/450μF plus one 400V/560μF, and the 850W model uses one 400V/470μF plus one 400V/680μF.


Seasonic PRIME Titanium 650W - Internal View

Technologically, the topology of the PRIME units is not alien by any of today’s standards. The primary inversion stage is a full bridge supported by an LLC resonant converter, and the secondary conversion stage is a synchronous rectifier that generates the 12V line, with DC-to-DC circuits for the secondary voltage lines. Seasonic managed to reach 80Plus Titanium efficiency standards simply by the proper selection of high quality active parts that have minimal thermal losses and cooperate well with each other. The flip side of this is the cost, which we will get to later. 


Seasonic PRIME Titanium 750W - Internal View


Seasonic PRIME Titanium 850W - Internal View

Introduction, Packaging & Bundle Cold Test Results: ~25ºC
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  • GhostOfAnand - Friday, April 7, 2017 - link

    High-efficiency is only one perk. The superlative ripple, transient response, etc of these Seasonic units means you're providing your high-end components with quality power. This means longer life, better stability, and greater over-clocking headroom.

    A solid PSU is the cornerstone of a proper build done right.
  • Arbie - Friday, April 7, 2017 - link

    Written like a true non-engineer.
  • Kevin G - Friday, April 7, 2017 - link

    The price difference would pay for itself in 7 years and considering that this unit has a 12 year warranty, the difference certainly would pay for itself. There are also additional factors to consider if say electrical prices increase. Return on investment would occur sooner under such a scenario.

    The real challenge is if motherboards continue to adhere to the ATX power spec for another decade. Using this power supply down the road could be challenge in that context. To these models credit, it is fully modular so if an ATX replacement were to arrive without adding any additional voltages (i.e. using only 3.3V, 5V and 12V), then an adapter cable could be created.

    These are appear to be excellent units worth the price premium they command.
  • DanNeely - Friday, April 7, 2017 - link

    It's not just the whole ATX standard, but all the stuff around it that would make me leery of planning on more than a half dozenish years from a PSU for deciding if the premium is worth it. We've been ATX for the last 20ish years during which time we've gone from 3.3/5V centric to mix low/high voltage centric, to 12V centric designs. Extra CPU power has gone from 6 pin 3.3/5V to a 4pin 12v to 8 pin 12v. Peripheral connectors have gradually gone from Molex to Sata. GPU power has gone from a 4pin Molex to 6pin to 8 pin. While an older PSU may work with suitable adapters (only the CPU connectors and 3.3/5 vs 12v centric designs are breakers); doing so becomes progressively more of a kludge.
  • JasperJanssen - Saturday, April 8, 2017 - link

    Yeah, but there's no reason whatsoever to think that we're going to move away from 12V centric any time soon, or ever. It's possible that we're going to drop legacy rails such as 3.3 and 5 like we did -5/-12 (already mostly gone), but I don't see us moving from 12V centric to 24V centric or 48V centric, even if that would give further efficiency advantages, and I don't think the 12-to-1.1V DC-DC converters are meaningfully less efficient than 24 or 48 to 1.1V -- so the possible gains are mostly in using less copper for the current carrying capacity. I don't see that as enough of a gain to overcome the inertia of the whole industry.

    Plus, the desktop PC industry is dying anyway, and when you're slowly dying is not usually the time to reinvent whole parts unless that can prevent the slowly dying.
  • Aslan7 - Monday, April 10, 2017 - link

    A friend upgraded their qx6600 systen 3-4 years ago, and I got the guts (MB, CPU, RAM) of the old system. Another friend was retiring a Micron Millennia PIII system from ~1997. I was planning to use the qx6600 guts in the Micron Millennia case, but as I was looking at it, I would have needed a massive number of power adapters to be able to plug things in. I said fine, so what?, but then I looked at the 12V output on the PSU. I was short amps. It wasn't even worth buying the adapters to try it. I threw away the guts of the Micron Millennia including the PSU. In short it's going to be a rare 90's power supply that has enough 12V amps that it would be usable today even with adapters.

    The Micron Millennia case though, is very well designed. The fans clip in and swing out of the way on hinges, there's fans where they're needed. The drive arrangement is nice, the PSU is mounted on a hinge to make cable routing easier. There's plenty of drive bays. All the proper standoffs are there for a large motherboard. It's a really good case especially being from 1997. The only two issues were the power button quit working about 2 years ago, so I have a power button cable run between the side panel and the case, and the other issue was the standoffs for the motherboard are insanely long. I had to special order those so that I had enough to support my large motherboard.

    I run a number of personal systems 24/7 doing various tasks for me and while idle performing computations for WorldCommunityGrid.org (curing cancer and such) My main system was powered by a PSU from ~2000. It was rated at 250 and I was pulling somewhere between an estimated 330 and 390 watts 24/7. It felt like it was spitting fire from the exhaust. To the credit of the Chinese no brand power supply it lasted for 16 months running 24/7. To replace that I bought an Enermax Platimax 80+platinum power supply, and about the same time I bought another 80+ platinum power supply for the qx6600. The energy savings have been noticeable with both, and they're cooler and quieter. Sorry, I don't have solid numbers to share,but I'm certain I've saved a large portion of their costs. The frustrating part is seeing reviews for 80+titanium power supplies at less than half the cost of some of the power supplies I bought.

    I'm really glad 80+titanium power supplies are happening, but why now? What changed to make these possible? Couldn't these have been made back in 2000? Why weren't they? Or are things honestly that much better manufactured today?
  • SkipPerk - Wednesday, May 3, 2017 - link

    I have often felt the same way, and I think it is just that now that prices have fallen so much, branding matters more. Also, the entire clear PC window case thing has people caring about aesthetics more.

    That said, modern PSU's are truly better than they have ever been. I am rocking and loving a Seasonic, and it is amazing just how good these new PSU's are. Your Platimax will likely last until the standards change.
  • HomeworldFound - Friday, April 7, 2017 - link

    For a power supply that has a 12 year warranty, that saving is pretty good, it'll last that long. It usually costs me a lot more than that, I get all of my power supply cables individually sleeved.
  • poohbear - Friday, April 7, 2017 - link

    Nobody buys these for the savings, they buy it for the rock solid performance when all your components are overlooked to their limits!
  • Gastec - Saturday, August 15, 2020 - link

    I compensated by consuming less Kentuky Fried Bourbon for one year.

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