Originally Posted by Krusher33
Can you elaborate please? What did the review not show that you're looking for?
40A on four +12 V rails equals 1920 W total. He's saying that if it can draw 40 A on each rail, it should be able to do far more than 850 W, thus it is underrated.
In reality though, it's probably just to get around the single-rail vs multi-rail thing by allowing a LOT of power on each rail, but still having a low total max power draw. So by using these specs, each rail is rated for 480 W and probably has OCP slightly above 40 A, meaning that you won't be in a situation where you accidentally end up with the majority of your power draw on a single rail that can't supply enough wattage (which you might risk if you tried to draw 300 W (HD 7990 comes to mind at this power level) from a 20 A rail (20 A x 12 V = 240 W). However, even though the PSU is rated for far more when the rail ratings are combined, there's most likely still OCP if you draw more than ~1000 W on all the rails combined.
The rating on individual rails probably isn't that important and you should just look at the total rating.
Edited by B!0HaZard - 9/3/13 at 9:39am