Our cross loading procedure is designed to rigorously test the stability of the main two rail combinations. We push the maximum rated current and wattage through the 12 volt rail(s), and then through the 3.3 and 5 volt rails combined, and see if the power supply is capable of delivering its specification for those. However, meeting the specification is not enough, the power supply must also maintain strong voltage regulation and noise/ripple to have “passed the cross load test.
The cross load test is a “worst case scenario” for the two main power delivery rail mechanisms (12v and 3.3+5v) and so the power supply will always deliver slightly lower than realistic/expected results. However, this is not necessarily a realistic test and it is just a case of pushing a power supply’s rails right to their rated limits to see how well they can hold up.