Seasonic S12 500W Power Supply

Interior of the S12 500W:

Seasonic has really crammed a lot into a standard sized PSU chassis. The design is somewhat different from any other PSU we have seen thus far. Remember, this PSU does have active PFC, which gives about a 99% Power Factor (PF) under typical usage.

Checking the bottom of the PSU, we can verify that there are indeed two separate 12V rails. 12V2 has the 8/4pin +12V connectors, while 12V1 has all the other connectors.

How We Test Power Supplies:

In order to thoroughly test a power supply we have built a special rig that is capable of dynamic load levels on each rail. A short article covering our power supply testing methodology in detail can be found here. Please read over the guide if you haven't already, you might just learn a thing or two. Simply plugging a power supply into a regular PC for "testing" is not accurate by any means, nor can any useful numbers be extracted by testing that way.

Also worth reading is our power supply primer article titled, Powering Your PC: Truths and Misconceptions - A Guide To Power Supplies, which covers how power supplies work in great detail.

If you have read the power supply testing article, you know that we publish four (4) groups of numbers for each power supply to give a simplified overall representation that can be compared to other power supplies. Many other load ranges are tested (but not published unless there is a serious problem) to ensure voltage levels remain within ATX12V specifications. I like to refer to it as "working the switchboard" since it involves flipping lots of switches tied to resistors on each rail to achieve various loads. Unfortunately we can't always dial in exact maximum numbers because of the fixed levels of resistance, but load levels we test are often far in excess of any load a regular PC will create.