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Seasonic S12 500W Power Supply - Page 3 of 3
Posted: February 02, 2005
Author: JimBowy
Manufacturer: Seasonic
Source: Seasonic
Comment or Question: Post Here

Test System:

The Seasonic S12 500W power supply was benchmarked in two stages, with voltages taken at idle and load. The power supply was connected to the test system (specs listed below) and voltages were taken using two methods. First, we tested the voltages directly from the 20-pin motherboard connector (which we believe to be most accurate). A Cen-Tech (Model P30756) multi meter was used to test the power supply with the black lead touching a black wire on the motherboard connector and the red lead moved to the respective voltage line. (yellow being the 12.0v line, red the 5.0v line, and orange the 3.3v). The second method of line monitoring was performed using a popular Windows software called Motherboard Monitor 5 (MBM5) This test system required using every available molex connector to power the components listed below. If SATA hard disks were installed in your system, this would free up at least two additional 4-pin molex connectors.

System Specifications:

AMD Mobile Athlon XP2400+ @ 2.4GHz (1.75v) Processor w/Thermalright SLK947U and 120mm Vantec Tornado (2,000rpm)
DFI nForce2 Ultra Infinity 400 Rev. A
2x 512MB Corsair TwinX PC3200 Memory (OC 'ed to 240FSB*10, 2.8V)
2x Maxtor 80GB Hard disks in RAID-0
1x Optical Devices (CDRW)
ATI Radeon 9800 Pro 128MB Videocard
Vantec 92mm Tornado Fan at 4,800rpm
1x PCI Device (Highpoint RocketRAID 454)
Antec Performance One P160 (Super Mid Tower) Case

Performance and Results:

After the power supply had been installed for a few days, we recorded the average voltages at idle and load. Please note all benchmarks were made with the FSB overclocked to 240MHz. Load was simulated by running the distributed computing tool known as Folding@Home. Load voltages were only taken after stressing the computer for a minimum of one hour. Here are the average idle and load voltages taken directly from the 20-pin motherboard connector. The lack of power fluctuations in this Seasonic power supply were surprising, none of the fluctuations exceeded 1% which is quite impressive considering the industry standard is +/- 5%.

For comparison purposes, we put the Seasonic S12 up against a reputable Antec 430W power supply on the same test system. Both power supplies did a very good job at remaining well within their specifications. When graphed, the results are close, demonstrating the good job both companies have done to stay well within the previously mentioned industry standard. The Seasonic S12 was closer to the "perfect" line voltage than the Antec in both the 12.00V and 5.00V lines. It was only on the 3.30V line the Seasonic was substantially "off" the target. However, this deviation was only 3% which is still very good. The 3.3 line was the only place where the Antec seemed to have a slight edge on the Seasonic S12.


The Seasonic S12 500W power supply provides plenty of power and extras to keep even an enthusiast happy. The unit complies with the latest ATX 12v 2.0 specifications while providing support for pci-express and utilizing active power correction (power saving technology). However, the features list continues as Seasonic decided to include the convenient Easy Swap connectors, quiet 120mm fan, support for dual processor systems, and the doctor cable management system. On top of all that, the power supply performed flawlessly with none of the line voltages (12, 5, and 3.3v) fluctuating more than 1%.

The Seasonic S12 500W power supply demonstrated stable voltages when comparing the load and idle voltages. With fluctuations of less than one percent and a three-year warranty, this power supply earns 4.5/5 stars.

Final Rating (4.5 out of 5 stars):


Easy Swap Molex connectors
More efficient APF (Active Power Correction) design
Quiet 120mm fan
Line voltage fluctuations of no more than 1%


Doctor Cable is not very attractive
Two more 4-pin molex connectors would be a nice addition (our system used all provided connectors)

Special thanks to Seasonic for providing the 500W S12 Power Supply to for review!

Please drop by the forum and feel free to discuss this review!

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