Yes but that's at 5V. 5V at 550mA is 2.75W. Times 2 is 5.5 watts. 12V at 1A is 12W. With switching supplies getting up around 70-80% efficient, you easily get 10W from your 12W supply.

If you were using linear regulators and running 5V at 1A from a 12V supply you'd be dissipating (wasting and turning into heat) about 7W.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)