Because he called me wrong then started spreading fud. I would never trust an answer from someone who has no fucking clue what they are talking about.
We might be speaking different languages here.
I was saying that his whole methodology was wrong, but that the OP's power supply should be able to support the card. He said the card could support it. The recommendation was fine even if the rationale was not.
The "I don't see why this is so difficult part" is about understanding efficiency. People seem to want to apply 80% efficiency twice: both to power drawn and power output. Several people just don't get it. Except none of that is really relevent to this discussion. They have no idea what efficiency means even if it is so simple a concept.
If you draw 6,000 watts but only output 600 watts to the components you're at 10% efficiency. WOW THAT'S TERRIBLE. However, your power supply would be rated at 600 watts so you are able to deliver 100% of your rated claim on a good power supply. Even at 10% you can deliver 600 watts to your components. Efficiency is irrelevant to the amount of power a power supply can supply (wow that sentence sounds strange...how much wood could a woodchuck chuck if...).
People see "80% efficient" and apply it twice, even though that is the wrong way to look at it. They assume that the power supply can only access 80% of the power it draws from the line, and then is only able to deliver 80% of that power to the components. That indicates 64% efficiency, not 80%, but math is evil so let's ignore it. So they create false constructs and make unfortunate facts true in their little own world. 80% efficient, though, means that a power supply delivers 80% of the power it draws from the wall to the components. There is no intermediate bullshit.
A good power supply is fully capable of supplying 100+% of its rated power for a while. The [H] torture tests at 80% for 8 hours because 8 hours is a long time and you lose efficiency and maybe even capability the longer you go. That said, how many people game for 8 hours in a row? If you're loading your PSU to close to 100% but only for 2-3 hours at a time it probably will not die.
My language has probably gone back and forth but I don't blame you for anything. I quoted you just because you provided a point of discussion.
For the people that believe a power supply can only deliver 80% of what it is rated for, that's not necessarily a bad metric, if you run at 80% 24/7. It's better to be safe than sorry, and you don't wan't to kill your PSU. The thing is that most people do not do that. Most (high-end) people stress their computers for a while when gaming then go back to normal use, which requires far less than 80% power use. Rock the shit out of that 5970 on an HX620.