The answer is yes. The power supply provides 3.3 volts, but still provides the other voltages, +/-5 and +/-12, as always. The 3.3 volts has it's own lines in the chassis main board. The chassis still uses 5 volt signalling, which is what most PCI boards expect. There are some new boards that are 3.3v but require 3.3 volt signalling as well. Most of these are "5v tolerant" meaning they can use 5v signalling without problem. Only boards that are 5v tolerant should be used in the MAGMA Expansion chassis as they may not function properly, or at all, with 5v signalling.