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.

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

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Figure 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.

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Figure 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.

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Figure 4: Cables

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