Seasonic X-Series KM3 650 W Power Supply Review

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Introduction

Seasonic is releasing the third generation of their power supplies with the 80 Plus Gold certification, dubbed the X-Series KM3, using a completely different internal design. So far, three versions were released, 650 W, 750 W, and 850 W, all with a single +12 V rail and a fully modular cabling system. Let’s see how the 650 W model fared on our tests.

Seasonic X-Series KM3 650wFigure 1: Seasonic X-Series KM3 650 W power supply

Seasonic X-Series KM3 650wFigure 2: Seasonic X-Series KM3 650 W power supply

The Seasonic X-Series KM3 650 W is 6.3” (160 mm) deep. It uses a 120 mm ball-bearing fan on its bottom (Sanyo Denki San Ace 120 9S1212F404). This fan is different from the one used on the Seasonic X-Series KM3 650 Wi. The power supply has a “hybrid/normal” switch that allows you to configure the fan to turn on only when the power supply load reaches 30% of the unit’s labeled wattage (i.e., 195 W), so the power supply won’t make any noise when the computer doesn’t demand a lot of power. Under the “hybrid” mode, between 30% and 50% load the fan will spin at a lower speed, generating lower noise than usual.

Seasonic X-Series KM3 650wFigure 3: Fan

The modular cabling system from this power supply has 13 connectors: two for the main motherboard power connector, six for video card and ATX12V/EPS12V connectors, and five for peripheral and SATA connectors. This power supply comes with the following cables:

  • Main motherboard cable with a 20/24-pin connector, 23.6” (60 cm) long
  • One cable with two ATX12V connectors that together form an EPS12V connector, 25.6” (65 cm) long
  • One cable with one EPS12V connector, 25.6” (65 cm) long
  • Two cables, each with two six/eight-pin connectors for video cards, 21.6” (55 cm) to the first connector, 3.9” (10 cm) between connectors
  • Two cables, each with four SATA power connectors, 15.7” (40 cm) to the first connector, 4.7” (12 cm) between connectors
  • One cable with two SATA power connectors, 12.6” (32 cm) to the first connector, 4.7” (12 cm) between connectors
  • One cable with three peripheral power connectors, 15.7” (40 cm) to the first connector, 5.1” (13 cm) between connectors
  • One cable with two peripheral power connectors, 11.8” (30 cm) to the first connector, 5.1” (13 cm) between connectors
  • One adapter to convert a standard peripheral power connector into a floppy disk drive power connector

All wires are 18 AWG, which is the minimum recommended gauge.

The number of connectors is very good for a 650 W power supply, allowing you to install up to two high-end video cards that require two auxiliary power connectors each.

Seasonic X-Series KM3 650wFigure 4: Cables

Let’s now take an in-depth look inside this power supply.

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Author: Gabriel Torres

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.

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