Enthusiast PC power supply questiuon

[ambam]

Which is better for high-end multi-GPU gaming computers, single or multi-rail power supplies?

What is the difference between the two?

I'm building an enthusiast gaming rig which is almost complete, it has dual SLI GTX 680's, a 3770K CPU, and 16GB DD3 1600MHz RAM. Please recommend the best PSU in your expert opinion.

 

[manofchalk]

Single rail is just better.The rail within a PSU I guess you could liken to a "source" of power. The 12v rail deals with supplying 12v power, the 5v rail deals with 5v, etc, etc.
Sometimes in a PSU there are multiple 12v rails, for reason I am not entirely sure of but I imagine its cheaper. Usually the sum of each rails power (Voltage x Amps) equals roughly its rated (on the box) wattage. However if it was a single rail PSU, then that one rail would be able to supply the entire rated wattage.

Having multiple rails means you have "weaker" rails than can supply less power each, so its possible to overload a rail (lets say with two GPU's on one 12v rail, CPU on the other) while still drawing under the PSU total power output. With a single rail PSU, you don't have to worry about that.

Just go for the usual brands, Seasonic, Corsair and XFX. For a dual GPU setup, would say 750W (850W if on LGA2011 or AM3+ and intend to overclock).
Just about the best supply you can get would be the Seasonic X750.