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Volts x Amperes = Watts

post #1 of 3
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So we all know that Volts x Amperes = Watts but that doesn't seem to make sense

For example taking a Frotron 400watt PSU with +3.3V@22A, +5V@21A, +12V1@18A, and +12V2@16A

3.3v x 22= 73watts
5v x 21= 105watts
12v x 34= 408watts
total= 580watts

But that is way more than 400watts... Am I missing something here??? Is it just the max watts each rail can have but they really are lower and average out????

Also is the Froton good???? Is 400watts too low??? If I consider overclocking and upgrading.????
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post #2 of 3
Power can also be calculated as Watts = Volts^2 / ohms which is a more realistic approach.

The way you are approaching it the PSU can supply 580 watts of power into a 0 ohm load before it burns up.

Power output from a PSU is always going to depend on the load resistance.

I wouldn't get anything less than a 520w 'Quality' PSU these days with PCI-E and especially if you are going to do any OCing and or Upgrading and at least a 600 if you are going SLi.
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post #3 of 3
you don't just add the 12v1 and the 12v2 together, thats the max amperage they can handle at any one time. As they both come from the same transformer,and the combined amperage is say 24a (which it isn't i don't think), and say if 12v1 takes say 13a, 12v2 can only use 11a.

you get me?
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