Originally Posted by Belial
So would you say in a 'perfect' situation, you COULD do that equation, but the lesser the quality of the PSU's, the less the wattage relates to the amps on the 12v rails?
i mean there is obviously a relationship - higher quality PSU's have a larger amount of amps and watts on their 12v rails than crappy ones. Maybe the equation I mentioned isn't exactly correct, but it does seem to have a correlation to the 12v rail power.
No -- in a perfect situation, the sticker on the PSU will clearly state what its output capability at +12V is, leaving no room for doubt or forcing you to do math to figure out what your PSU can or cannot do. You should never add up the amperage ratings for several +12V rails. While the result may sometimes match the PSU's actual capabilities, in most cases it won't, and just because it sometimes does does not mean anything
Look at the Antec TP-750 for example. It has four +12V rails, each rated for 25A. Obviously you can't add those up for a total of 100A, or you'd have a 1200W PSU. The ampere ratings on the sticker tell you how the OCP is calibrated on each rail, not how much total power you can get out of the PSU.
And none of this really has anything to do with quality, except as applied to the trustworthiness of the sticker. If the sticker somehow omits the "total wattage" information, then something's up. If the sticker does have the info, then it depends on the brand whether you can trust the sticker or not