The big 12v rails do come at a cost though, the 3.3v and 5v rails
are quite a bit lower than those on the power supply it replaced (12 amps
and 6 amps lower respectively to be precise) but then comparing it to its
competition of a similar rating its right on a par on the power rating of
the 3.3v and 5v rails.

http://www.xtremecomputing.co.uk/review.php?id=450