my supply is switching power supply 400-atx
That is not what I said. Virtually all PSUs are switching mode PSUs. What I said was continuous power
meaning the PSU can supply the rated/said wattage with in the ATX specification at 40-50C ambient temp/hot box temp. For example, all Corsair,PC Power units and some Antec units use this wattage in their advertisements which is the correct wattage to use, others state the MAX wattage for the PSU.