PSU Question

[Malo]

I'm hoping someone might be able to clear up something for me. How is the output ampage on a PSU calculated for a 12v rail when considering the 26a req on a 8800gts? I assume it's not the amps on a single 12v line as not even a $360 galaxy psu meets that req. Is it the total amps output on all 12v lines?

I bought a true power trio for my wife's new pc which has 12v lines at 19a each, with a max output of 624 watts on the 12v lines. Is that effectively 52a max output? And if so, does that mean it's not recommended for 2 8800gtx which require 30a each?

 

[Frank]

The simple answer: no, the maximum output is lower than the maximal values for each line. And the rated maximum on your card will never be needed.

A good 450 watt PSU is good enough in any case, and a cheap 700 watt PSU as well. You probably need less than that, depending.

 

[Malo]

Well my main question was how do you determine what would be sufficient for 8800 series cards with the 26a requirement. Yeah you've stated that a 450w is usually enough, same as a cheap 700w, however how is it actually determined?

People always say just have a high watt psu, so why the stress on the 26a or 30a for the new nv cards? Why don't they just say "500w+" or something? I'm assuming because the ampage output varies so much on PSUs. Which is why I'm trying to clarify how you actually determine the capable output of a PSU in ampage for the 12v line?

 

[Frank]

The problem is, that there are very many different ways to build a PSU. If you look at the top rated ones, they all do things quite differently. But in general, they deliver what they state.

For the cheap ones, there are very many different builds as well. And they generally tend to use their theoretical peak figure for their stated power.

So, the only useable way to make sure is: buy a good one. You can trust them to deliver according to their specs. For the cheap(er) ones, it is a lot more difficult. And only a very few review sites have the equipment needed to measure them.