this is the only negative I could find for the saesonic. what would the 24-20 pin con be used for and why do they need one?
Overall, the new Seasonic S12-600 power supply produced very good results. The unit exhibited good voltage regulation with excellent stability and offers a lot of capacity on the +3.3V, +5V and dual +12V rails. The S12-600 is very quiet even when operating under a moderately heavy load and runs cooler than most.
The S12-600 uses active power factor correction and produced one of the highest overall efficiencies I have measured to date. Seasonic is to be congratulated for developing a line of power supplies that are both environmentally friendly (active PFC) and highly efficient (>80%).
On the down side, the main output voltages were a bit low when using the 24-pin to 20-pin ATX adapter cable. Even so, all measured voltages were still within the required ATX12V specified tolerances.