aren't the quad fx amd systems the only ones that even draw more than 500W??? A decent 600-700W psu is the absolute maximum that anyone should ever consider. The system in my sig can be powered by a single 300W psu.

damn i could almost run a welder off one of those

newtekie1RickyG512, lets see here, who am I going to go with here, random people on a forum that say one rail with 150A is better, or the people that make the standards and have been researching and learning about the issue for years who say that a single rail shouldn't have more than 20A?

Which would you go with?

The main issue with dual rials is that some manufacturers where labeling the rail by there max power draw they where fused for. Lets say you got a PSU with dual rails that where rated both at 15a. You would assume there would be 30a total, thats where the problem comes in. The 15a is only where the over current kicks in on each rail. The power is really draw form one transformer[ lets say 24a] and then divided by over current protection at 15a each. So you max draw is really 24a but you can pull 15a off of each rail just not at the same time. A lot of manufacturers now suggest single rials[ ATI/AMD for one]and many PSU makers have given up certifications to put all the current on one rail. The 20a limit was there to prevent burnt pins due to over current but it was solved by adding more pins[ 24 an 2x2 also the 8 pin cpu] to draw power form. There are true multi rail PSUs that have separate circuits and provide more then just two fused leads, like better stability under load. The dual rail movement got a bad rap and it was not just because of the low enders, some trusted names where doing the same thing.

Dual rail seems like it could be marketing trickery to advertise 2x15 when really it's 24/2 = 2x24 (as in unsmart's example) but the "average idiot" customer wouldn't think that far. I could see the benifit of dual rail as one surge from one rail wouldn't cause dropouts in the other IF the 2 rails had proper independant regulators and filter caps to address the surges.

I have a single Antec trupower 480w running a prescott o/c'd from 3.4 to 4ghz, 512mbx4 ddr-2, 4 sata harddrives, 2 dvd/rw combo drives, 6 case fans and a single x1950 pro. Not a bad accomplishment for a 480w. I added a thermaltake powerexpress 250 now that I have crossfire. The 480w wouldn't have ran like that forever -but- the fan controller in the psu doesn't seem to think the temps are that high because it's sitting at 950rpm. A name brand 550 would seem more then enough for the average user running a single highend card like a x1950xtx. For SLI or Crossfire I would suggest a 650-800w depending on how much other crap is running off it.