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Seasonic X-Series 850W KM3 Power Supply Review

Rating: 9.5.

Seasonic have been consistently releasing some of the finest power supplies for the enthusiast audience this year. This is the reason why their designs are often used by respected companies such as Corsair and BeQuiet! Part of the Seasonic strategy is always to keep an active refresh schedule in place. With this in mind we are analysing their latest KM3 850W model today, the replacement for the award winning KM2 which we reviewed back in September.

The X-Series 850W KM3 is not just a simple refresh however, the internal design is completely different and we will take a look at this shortly. The KM2 was already a very impressive power supply so we are interested to see how far the company can push the new design.

They have three models already in the KM3 range, a 650W, 750W and 850W model all with a single +12V rail, fan controller and new modular cabling.

Special Features –

  • 80PLUS® Gold Certified Super High Efficiency
  • Full Modular Cabling Design
  • Patented DC Connector Module with Integrated VRM [Voltage Regulator Module]
  • DC to DC Converter Design
  • Seasonic Hybrid Silent Fan Control
  • Sanyo Denki San Ace Silent Fan
  • Conductive Polymer Aluminum Solid Capacitors
  • Highly Reliable 105℃ Japanese Brand Capacitors
  • Tight Voltage Regulation [±1%]
  • Active Power Factor Correction [99% PF Typical]
  • High +12V Output
  • High Current Gold Plated Terminals
  • Dual Sided PCB Layout
  • Ultra Ventilation [Honeycomb Structure]
  • Multi-GPU Technologies Supported
  • All-in-One DC Cabling Design
  • Easy Swap Connector
  • Universal AC Input [Full Range]
  • 7 Years Warranty

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  • Ian

    They do rock, no doubt about it !

  • Barry M

    Very nice indeed. id like to see a review of their 650W or 750W, 850W is a bit overkill for me…… coming soon?

  • Mannucuna

    I like the sleeved cables 🙁 didnt know people like the flat ones more…..

  • Warren

    @ Mannucuna.

    Flat cables are better for routing, some cases have problems housing the fatter cables behind the motherboard tray. I do agree however, the sleeved cables look better, but most people dont want to be looking at them… especially in a windowed case. Its an industry wide move, Seasonic were slow to adopt them.

  • Xtreme

    its confusing because most of the stores dont list these as KM2 or KM3, its a complete guess when they dont include images or detailed information,. they should clearly mark these R3 on the box on the front.

  • GeneO

    Yes the marketing is confusing. newegg has been shipping the for a while but had the images of the KM2 model.

    Minor nitpick about the review. It says “four OCP channels, two for +12V, one for +5V and another for +3.3V”

    which makes it sound like it is a two rail PSU. I believe it is a single rail and, like its predecessor, one of the two 12V OCP channels isn’t populated or used.