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Seasonic S12D-850 850W Power Supply Review
Seasonic S12D-850 850W Power Supply Review  - PCSTATS
Abstract: Of course there's more to the S12D 850 than just the amount of juice it can produce. This power supply is 80 Plus Silver efficiency certified, which guarantees that it operates at above 85% efficiency across 20%, 50% and 100% loading.
 85% Rating:   
Filed under: Power Supply Published:  Author: 
External Mfg. Website: Seasonic Sep 20 2009   J. Apong  
Home > Reviews > Power Supply > Seasonic S12D-850

Power Supply Load Tests

Power supplies which employ Power Factor Correction (PFC, or A-PFC) help ensure efficient conversion of AC to DC voltage, and reduce the amount of energy wasted as heat. That means a quieter 120mm fan can be used, and less noise for your ears.

PCSTATS tests power efficiency with the aid of an Extech Model 380803 Power Analyzer. The meter is located between the mains 120AC supply and the power supply, and a 120W dummy load is connected to the power supply being tested. Power jitter is measured with a Mastech MS8230B Multimeter at the device power connectors. The test apparatus and power meters are shown below.

The power supply looking device is actually the 120W dummy load. To the right is a standard Voltmeter, and in the background the Extech Model 380803 Power Analyzer (with readings for Watts, PFC/KHz, source voltage (AC) and Amperage).

Power Jitter Observations - Motherboard

Voltage jitter is read by accessing the power options displayed in the motherboard BIOS, with the system obviously in an unloaded state. Voltages were read from the BIOS of an Foxconn Mars Intel P35 motherboard.

Power Jitter Observations - Motherboard

Listed Voltages

Lower Voltage

Upper Voltage














There were next to no fluctuations in power when the S12D 850 was plugged in to the motherboard, which speaks well for the PSU's use in systems that are built for tweaking or overclocking. Having a stable input voltage from the power supply is critical if you're going to be over-volting the processor or system components.

Seasonic Load Tests Source: Seasonic

When looking at the Seasonic Power Supply test results we see two values, wattage and volt-amps. Since it might not be clear what they measure, here's a brief overview.

The volt-amp (VA) value is how much real power is being consumed by the power supply being tested to provide the wattage (W) value. The higher the VA value is, the more electricity is being used by the power supply. Because no electrical device is 100% efficient, there will always be some loss when converting AC to DC. The closer the volt-amps and wattage figures are to each other, the more efficient a power supply is. This is called the Power Factor: wattage / volt-amps =PF.

Since we're testing with a 120W dummy load, the load on the power supply (wattage) should be as close to this figure as possible. Anything above this load in apparent power describes the overhead and wasted energy (given off as heat) for the particular power supply being tested. For the unloaded tests, the wattage and volt-amp figures should be as close as possible to one another. The lower the figures are, the less power is being wasted.

Measurements were taken with an Extech 380803 Power Analyzer.

Seasonic Power Load Tests
Power Supply Model Wattage Test Type Loaded Unloaded
Seasonic SuperTornado 400 W
Active Power 177 W 6 W
Apparent Power 182 VA 7 VA
Vantec iON2 350 W Active Power 192 W 10 W
Apparent Power 277 VA 21 VA
Antec TruePower 330 330 W Active Power 195 W 22 W
Apparent Power 289 VA 38 VA
Ultra X-Connect Green UV 500W 500 W Active Power 193W 22 W
Apparent Power 307 VA 40 VA
AOpen Silent Power AO400-12AHN 400 W Active Power 179W 9 W
Apparent Power 275 VA 18 VA
Seasonic S12-430 430 W
Active Power 179W 6W
Apparent Power 180VA 9VA
PC Power and Cooling Turbo-Cool 510 Express/SLI

510 W

Active Power

200 W

29 W
Apparent Power 202 VA 32 VA
HEC Ace Power 580UB

580 W

Active Power

183 W

12 W
Apparent Power 272 VA 26 VA
HEC Win 550UB 550 W Active Power 184W 10W
Apparent Power 263VA 22VA
Akasa PowerPlus AK-P550FF 550 W
Active Power 194W 38W
Apparent Power 197VA 40VA
AOpen Prima Power AO700-12ALN 700 W
Active Power 172W 3W
Apparent Power 181VA 9VA
PC Power & Cooling Turbo-Cool 1KW 1000 W
Active Power 205W 25W
Apparent Power 207VA 32VA
Seasonic S12 600 600 W
Active Power 164W 7W
Apparent Power 173VA 9VA
Mushkin Enhanced XP-650 650 W Active Power 192W 22W
Apparent Power 279VA 43VA
Seasonic S12 Energy Plus SS-650HT 650 W
Active Power 150W 7W
Apparent Power 150VA 10VA
Seasonic M12 700W 700 W
Active Power 161W 8W
Apparent Power 165VA 11VA
Corsair HX620W 620 W
Active Power 171W 8W
Apparent Power 173VA 12VA
Zalman ZM600-HP 600 W
Active Power 173W 5W
Apparent Power 175VA 9VA
HEC Zephyr 650 650 W
Active Power 185W 12W
Apparent Power 190VA 17VA
GlacialPower GP-PS550BP 550 W Active Power 178W 6W
Apparent Power 269VA 17VA
Cooler Master Real Power Pro 750W 750 W
Active Power 158W 6W
Apparent Power 163VA 9VA
Seasonic S12 II 500W 500W
Active Power 145W 7W
Apparent Power 148VA 10VA
Enermax Infiniti 720W 720W
Active Power 179 W 12 W
Apparent Power 181 VA 18 VA
Active Power 172 W 9 W
Apparent Power 193 VA 12 VA
PC Power & Cooling Silencer 750 Quad 750
Active Power 168 W 12 W
Apparent Power 175 VA 15 VA
Enermax Galaxy EGX850EWL 850 W
Active Power 184 W 11 W
Apparent Power 193 VA 16 VA
Seasonic M12D 750 750W
Active Power 169W 7W
Apparent Power 173VA 9VA
Seasonic S12D 850 850W
Active Power 148W 7W
Apparent Power 149VA 10VA

The Seasonic S12D 850 power supply draws 148W of power when a 120W load was hooked up, which is 81.1% efficiency, in line with its 80 Plus efficiency rating! Considering the high power capacity of this unit, the efficiency with only a 15% load is very promising.

If the amount of load was ramped up closer to the 850W capacity of the S12D 850, we'd be seeing even greater efficiency here, likely approaching the 90% mark.

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Contents of Article: Seasonic S12D-850
 Pg 1.  Seasonic S12D-850 850W Power Supply Review
 Pg 2.  Appearance and Physical Specifications
 Pg 3.  Looking inside the Power supply
 Pg 4.  — Power Supply Load Tests
 Pg 5.  Efficient Power Supply Triumphs Vanity

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